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",isbn:"978-1-83968-930-7",printIsbn:"978-1-83968-929-1",pdfIsbn:"978-1-83968-931-4",doi:null,price:0,priceEur:0,priceUsd:0,slug:null,numberOfPages:0,isOpenForSubmission:!1,hash:"f159c09dab49a9bc6239b42660d8e8ec",bookSignature:"Dr. Yongxia Zhou",publishedDate:null,coverURL:"https://cdn.intechopen.com/books/images_new/10310.jpg",keywords:"Brain Science, Brain-Computer Interface, Imaging of Neural Networks, Brain Networks, Brain Function, Molecular Imaging, Brain and Mind, Functional Imaging, Multimodal Imaging, Neuroplasticity Enhancement, Learning, Memory",numberOfDownloads:null,numberOfWosCitations:0,numberOfCrossrefCitations:null,numberOfDimensionsCitations:null,numberOfTotalCitations:null,isAvailableForWebshopOrdering:!0,dateEndFirstStepPublish:"September 28th 2020",dateEndSecondStepPublish:"October 26th 2020",dateEndThirdStepPublish:"December 25th 2020",dateEndFourthStepPublish:"March 15th 2021",dateEndFifthStepPublish:"May 14th 2021",remainingDaysToSecondStep:"3 months",secondStepPassed:!0,currentStepOfPublishingProcess:4,editedByType:null,kuFlag:!1,biosketch:"Yongxia Zhou had completed her Ph.D. from the University of Southern California in Biomedical imaging (2004) and had been trained and worked as a neuroimaging scientist in several prestigious institutes including Columbia University, New York University, University of Pennsylvania. Her research interest is focused on neuroimaging and neuroscience applications.",coeditorOneBiosketch:null,coeditorTwoBiosketch:null,coeditorThreeBiosketch:null,coeditorFourBiosketch:null,coeditorFiveBiosketch:null,editors:[{id:"259308",title:"Dr.",name:"Yongxia",middleName:null,surname:"Zhou",slug:"yongxia-zhou",fullName:"Yongxia Zhou",profilePictureURL:"https://mts.intechopen.com/storage/users/259308/images/system/259308.jpeg",biography:"Yongxia Zhou obtained a PhD from the University of Southern California in Biomedical Imaging in 2004. Her main research interest is in radiology and neuroscience applications. She had been trained and worked as a medical imaging scientist at several prestigious institutes including Columbia University, University of Pennsylvania, and the National Institutes of Health (NIH). Her research focuses on multimodal neuroimaging integration including MRI/PET and EEG/MEG instrumentation that makes the best use of multiple modalities to help interpret underlying disease mechanisms. She has authored six monograph books, and edited several books for well-known publishers including IntechOpen and Nova Science. She has published more than 100 papers and presentations in many reputed international journals and conferences, and served as reviewer and editor for several well-known associations.",institutionString:"University of Southern California",position:null,outsideEditionCount:0,totalCites:0,totalAuthoredChapters:"2",totalChapterViews:"0",totalEditedBooks:"3",institution:{name:"University of Southern California",institutionURL:null,country:{name:"United States of America"}}}],coeditorOne:null,coeditorTwo:null,coeditorThree:null,coeditorFour:null,coeditorFive:null,topics:[{id:"16",title:"Medicine",slug:"medicine"}],chapters:null,productType:{id:"1",title:"Edited Volume",chapterContentType:"chapter",authoredCaption:"Edited by"},personalPublishingAssistant:{id:"247041",firstName:"Dolores",lastName:"Kuzelj",middleName:null,title:"Ms.",imageUrl:"https://mts.intechopen.com/storage/users/247041/images/7108_n.jpg",email:"dolores@intechopen.com",biography:"As an Author Service Manager my responsibilities include monitoring and facilitating all publishing activities for authors and editors. From chapter submission and review, to approval and revision, copyediting and design, until final publication, I work closely with authors and editors to ensure a simple and easy publishing process. I maintain constant and effective communication with authors, editors and reviewers, which allows for a level of personal support that enables contributors to fully commit and concentrate on the chapters they are writing, editing, or reviewing. I assist authors in the preparation of their full chapter submissions and track important deadlines and ensure they are met. I help to coordinate internal processes such as linguistic review, and monitor the technical aspects of the process. As an ASM I am also involved in the acquisition of editors. 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Multiple references and textbooks are needed to study these lesions. Herein we attempted to gather common pathological entities occurring in this region and describe the characteristics, clinical presentation, histopathology, diagnosis and management of each in one chapter. Epithelial tumors are presented first.
Common epithelial tumors of concern to oral and maxillofacial surgeons are: Inverted papilloma, Squamous cell carcinoma, Pleomorphic adenoma, Mucoepidermoid carcinoma, Sinonasal undifferentiated carcinoma, Adenoid cyctic carcinoma, Basal cell carcinoma and Verrucous carcinoma.
Inverted papillomas characteristically arise from the lateral nasal wall in the region of the middle turbinate or ethmoid recess, and often extend secondarily into the sinuses, especially the maxillary sinus. Nasal obstruction is the most common presenting symptom. Other manifestations include nasal drainage, epistaxis, anosmia, headaches (especially frontal), epiphora, proptosis and diplopia. Pain, on the other hand, is an uncommon initial complaint, occurring in only about, 10% of all cases. When present, it should always arouse suspicion of secondary infection or malignant change (Fig. 1).[1,2]
Inverted papilloma of the right nasal cavity and maxillary sinus.
Inverted papillomas are composed exclusively or almost exclusively of hyperplastic ribbons of basement membrane-enclosed epithelium that grow endophytically into the underlying stroma. Infrequently, a minor exophytic component may be seen. The epithelium is multilayered, usually 5-30 cells thick, and formed of squamous or ciliated columnar (respiratory epithelial) cells admixed with mucocytes. Nonkeratinizing squamous or transitional-type epithelium tends to predominate, and is often covered by a single layer of ciliated columnar cells (Fig. 2).[1,-3]
Inverted papilloma low power photomicrograph. Note epithelial-lined, duct-like structures that endophytically project into the underlying stroma
Complete surgical excision is the treatment of choice. Inadequate excision of lesions probably accounts for the local recurrence rate of 22-50% [1-,3]
Squamous cell carcinoma (SCC) of the jaws or antrum is not an uncommon malignancy. It is largely of unknown cause but may be related to known carcinogens. However, unlike squamous cell carcinomas in other head and neck sites, squamous cell carcinomas of the paranasal sinuses have been associated only weakly with tobacco use. It occurs more often in men (2–5 times) and affects individuals with a mean or median age of 60 to 65 years. Signs and symptoms depend on the stage of the disease and direction of tumor growth. Early on, they are vague and often confused with other lesions. [1,3- 8] Complaints can be grouped into five categories: nasal, oral, ocular, facial, and neurological. Nasal manifestations include unilateral stuffiness, obstruction rhinorrhea, and epistaxis. Oral findings include pain referred to the upper premolar and molar teeth; loosening of the teeth; swelling or ulceration of the palate, alveolar ridge, or gingivobuccal sulcus; or a fistula. Common ocular features consist of swelling of the eyelids, excessive tearing, visual disturbances, and proptosis. Facial symptoms from involvement of the anterior wall of the sinus and are characterized by swelling and asymmetry of the cheeks. Neurological manifestations are often due to tumor infiltration of the branches of the fifth cranial nerve with subsequent numbness or paresthesia of the lips or cheek. Approximately 10% to 15% of patients present with positive regional lymph nodes, usually the upper jugular, submandibular and retropharyngeal. Distant metastases at the time of diagnosis, however, are uncommon [9-11] Clinically, it usually appears exophytic with an indurated margin. Extension into structures, such as the tongue, cheek, oral cavity, alveolus or palate, infratemporal fossa, and periorbital soft tissue, is not uncommon (Fig. 3). [1,3-8]
Squamous cell carcinoma ulcerated lesion of the hard palate
Computed tomography and MRI are indispensable, not only in determining the extent of disease, but also in assisting the surgeon in selecting the best operative approach (Fig. 4).
SCC of the right maxillary sinus.
The vast majority of squamous carcinomas are either well or moderately differentiated. Poorly differentiated tumors are less common (Fig. 5).[2]
Moderately differentiated SCC; small nests of squamous cells with central keratinization.
SCC of the jaws and oral cavity usually is treated by block resection and 1-2 cm free margins. Some cases are treated by radiotherapy or combined radical surgery and radiotherapy. However, even with radical treatment the prognosis is poor, with a 5-year survival rate of approximately 40%. The presence of metastatic deposits in local lymph nodes reduces the survival rate to less than 8%, as does involvement of the pterygopalatine fossa. With or without cervical node involvement, death usually occurs from local destruction and the inability to control the primary disease [1,3- 8] Because the tumors of the sinus are generally advanced at the time of diagnosis, a combination of surgery and radiation is used in most instances, with or without chemotherapy. Local recurrence, seen in about 30% to 45% (range 18–75%) of cases, is the most common cause of treatment failure and death. Virtually, all recurrences appear within two years of therapy and most within one year. During the course of the disease, 25% to 30% of patients will develop positive regional lymph nodes and 10% to 20% may experience distant metastases.[9,10,11]
Pleomorphic adenoma is the most common salivary gland tumor and accounts for about 60% of all salivary neoplasms[1,2,8]
Pleomorphic adenomas are usually slow-growing painless masses. Small tumors typically form smooth, mobile, firm lumps but larger tumors tend to become bossellated and may attenuate the overlying skin or mucosa. Pain or facial palsy is uncommon but are occasionally seen, usually in relation to infarcted tumors. The size of most tumors vary from about 2-5 cm but some reported cases have been massive. In the palate, tumors are usually seen at the junction of the hard and soft palate unilaterally. In the hard palate they feel fixed due to the proximity of the underlying mucoperiosteum.[2,8]
Pleomorphic adenoma shows a remarkable degree of morphological diversity The essential components are the capsule, epithelial and myoepithelial cells, and mesenchymal or stromal elements. The epithelial component shows a wide variety of cell types including cuboidal, basaloid, squamous, spindle cell, plasmacytoid and clear cells. Rarely, mucous, sebaceous and serous acinar cells are seen. These cells are cytologically bland and typically have vacuolated nuclei, without prominent nucleoli, and a low mitotic activuty. The epithelium usually forms sheets or duct-like structures. The mesenchymal-like component is mucoid/myxoid, cartilaginous or hyalinized and sometimes this tissue forms the bulk of the tumor (Fig. 6). [1]
Pleomorphic adenoma. A.Squamous differentiation B.Plasmacytoid differentiation. C. Chondroid differentiation.
Although pleomorphic adenoma is a benign tumor it can cause problems in clinical management due to its tendency to recur and the risk of malignant transformation. Therefore it should be removed with free margins and the adjacent bone i.e. hard palate (or a layer of bone i.e. cortex of mandible). Recurrences are rare in the minor glands but in a meta-analysis of parotid tumors 3.4% of tumors recurred after 5 years and 6.8% after 10 years with a range of 1-50%. Many recurrent pleomorphic adenomas are multifocal and some are so widely distributed that surgical control becomes impossible.[2]
Mucoepidermoid carcinoma is most common in the parotid gland and usually appears as an asymptomatic swelling. Mucoepidermoid carcinoma is the most common malignant salivary gland tumor in children. The minor glands constitute the second most common site, especially in the palate. Intraosseous tumors also may develop in the jaws. Pain or facial nerve palsy may develop, usually in association with high grade tumors. [1,2,8]. CT scan and MRI are essential prior to treatment (Fig.7).
CT scan of mucoepidermoid carcinoma in right maxillary sinus.
As its name implies, mucoepidermoid carcinoma is composed of a mixture of mucus-producing cells and squamous (epidermoid) cells The mucous cells vary in shape but contain abundant foamy cytoplasm that stains positively with mucin stains. The epidermoid cells are characterized by squamoid features, often demonstrating a polygonal shape, intercellular bridges, and. rarely, keratinization. In addition, a third type of cell—the intermediate cell is typically present and is believed to be a progenitor of both the mucous and the epidermoid cells. Intermediate cells vary in appearance from small, basaloid ("maternal") cells to slightly larger ovoid cells with scant, pale eosinophilic cytoplasm. Some tumors also show variable numbers of clear cells (Fig.8).[1]
High-grade salivary-type mucoepidermoid carcinoma cells, and rare mucinous cells exhibiting mild nuclear changes, cords and strands of squamoid cells and clear pleomorphism.
The treatment of mucoepidermoid carcinoma is predicated by the location, histopathologic grade, and clinical stage of the tumor. Early-stage tumors of the parotid can often be treated by subtotal parotidectomy with preservation of the facial nerve. Advanced tumors may necessitate total removal of the parotid gland, with sacrifice of the facial nerve. Submandibular gland tumors are treated by total removal of the gland. Mucoepidermoid carcinomas of the minor glands usually are treated by assured complete surgical excision with free margins. For low-grade. Neoplasms, only a modest margin of surrounding normal tissue may needed to be removed, but high-grade or large tumors warrant wider resection, similar to that required for squamous cell carcinomas. If there is underlying bone destruction, then the involved bone must be excised. Radical neck dissection is indicated for patients with clinical evidence of metastatic disease and also may be considered for patients with larger or high-grade tumors. Postoperative radiation therapy also may be used for more aggressive tumors.[1] The prognosis depends on the grade and stage of the tumor. Patients with low-grade tumors generally have a good prognosis. For most primary sites, local recurrences or regional metastases are uncommon, and around 90% to 98% of patients are cured. The prognosis for those with intermediate-grade tumors is slightly worse than that for low-grade rumors. The outlook for patients with high-grade tumors is guarded, with only 30% to 54% of patients surviving.[1]
Sinonasal undifferentiated carcinoma (SNUC) is a rare, highly aggressive, and clinicopathologically distinctive neoplasm of the nasal cavity and paranasal sinuses. The tumor was first described in 1986. Since then fewer than 100 cases have been reported. In the earlier literature, tumors of this type were probably reported as anaplastic or undifferentiated carcinomas. The histogenesis is uncertain; some investigators have theorized that the cell of origin may be related to the Schneiderian membrane or olfactory epithelium. The pathogenesis of SNUC is poorly understood. A few cases have been associated with a history of smoking or the presence of Epstein-Barr virus (EBV). Although a strong correlation with these factors has not been established. In some instances, patients have developed SNUC secondary to radiation therapy for nasopharyngeal carcinoma or retinoblastoma.[1,3-8]
Although a broad age range (3rd- 9th decades) has been reported, there is a tendency for older patients to be affected, with a median age at presentation being in the 6th decade. Men are affected more commonly than women, with a male to female ratio of approximately 2:1 to 3:1. SNUC is well known for rapid development of locally extensive disease. The neoplasm typically appears as a large tumor mass that can involve multiple regions of the sinonasal tract, usually including the nasal cavity, maxillary sinus, and ethmoid sinuses. In addition, extension into contiguous sites—such as the nasopharynx, orbit, and cranial cavity—is common. Inferior penetration into the oral cavity is possible as well. There is usually relatively rapid development of multiple sinonasal symptoms, including nasal obstruction, discharge, epistaxis, swelling, and pain. Orbital involvement may lead to proptosis, periorbital swelling, diplopia and vision loss. Cranial nerve palsies are a common finding as well. Radiographic assessment is best performed by CT or MRI, which typically reveals a large, expansile sinonasal mass with bony destruction and invasion of adjacent structures (Fig.9). [1-8]
Sinonasal undifferentiated carcinoma mass in the right maxillary sinus.
Sinonasal undifferentiated carcinoma is characterized by trabeculae, ribbons, sheets, and nests of polygonal cells with minimal cytoplasm and pleomorphic, hyperchromatic vesicular nuclei. No squamous or glandular differentiation should be observed. Mitotic figures are numerous. Tumor necrosis, apoptosis. and lymphovascular invasion are usually prominent. The surface epithelium overlying the tumor may exhibit dysplasia or carcinoma in situ. Immunohistochemical staining for cytokeratin or epithelial membrane antigen is typically positive (Fig.10). [1 -8]
Undifferentiated carcinoma neoplastic cells with characteristic, chromatically uniform, vesicular nuclei, with no evidence of squamous differentiation.
The standard approach has been aggressive multimodal therapy, including complete surgical resection when feasible followed by adjuvant radiation and/or chemotherapy. The prognosis for this lesion is extremely poor, with an overall 5-year survival rate of less than 20%. However, a few centers recently have reported promising results with induction chemotherapy followed by radiation and surgical resection of any remaining disease. This newer treatment approach has been associated with 2-year survival rates of 64% to75%. High-dose chemotherapy and bone marrow transplantation may extend the life of the patient. Local recurrence is common and is the major cause of morbidity and mortality. Metastasis is possible, usually to cervical lymph nodes, bone, liver, or brain. [1-8]
The adenoid cystic carcinoma usually appears as a slow growing mass. Pain is a common and important finding, occasionally occurring early in the course of the disease before there is a noticeable swelling. Patients often complain of a constant, low-grade, dull ache, which gradually increases in intensity. Facial nerve paralysis may develop with parotid tumors. Palatal tumors can be smooth surfaced or ulcerated. Tumors arising in the palate or maxillary sinus often show radiographic evidence of bone destruction of the hard palate with extension of the tumor into the nasal cavity and maxillary sinuses (Fig.11).[1-8]
Adenoid cystic carcinoma. Note destruction of the left maxillary sinus.
Three major patterns are recognized: [1] cribriform. [2] tubular, and [3] solid. Usually a combination of these is seen, and the tumor is classified based on the predominant pattern (Fig.12).[1-8]
Adenoid cystic carcinoma; cribriform variants may show tumor cell sheets containing cylindrical, pseudoluminal spaces.
Adenoid cystic carcinoma is a relentless tumor that is prone to local recurrence and eventual distant metastasis. Surgical excision is usually the treatment of choice, and adjunct radiation therapy may slightly improve patient survival in some cases. Because metastasis to regional lymph nodes is uncommon, neck dissection typically is not indicated. Because of poor overall prognosis, regardless of treatment, clinicians should be cautioned against needlessly aggressive and mutilating surgical procedures for large tumors or cases showing metastases. [1- 8]
Basal cell carcinoma (BCC), the most common skin cancer (and the most common of all cancers), is a locally invasive, slowly spreading, primary epithelial malignancy that arises from the basal cell layer of the skin and its appendages. Basal cell carcinoma is a disease of adult caucasions, especially those with fair complexions. Although most patients are older than 40 years of age at the time of diagnosis, some lesions are detected as early as the second decade of life, particularly in patients with red or blonde hair and blue or green eyes. Approximately 80% of lesions occur on the head and neck, with the remainder involving the trunk and limbs[1,8]
The basal cell carcinoma displays a considerable diversity of appearances under the microscope i.e. nodulocystic (noduloulcerative), superficial, adenoid, pigmented, infiltrative, morpheaform, and keratotic. The noduloulcerative pigmented, and syndrome-related basal cell carcinomas are comprised of uniform ovoid, dark-staining basaloid cells with moderate-sized nuclei and relatively little cytoplasm. The cells are arranged into well-demarcated islands and strands, which appear to arise from the basal cell layer of the overlying epidermis and invade into the underlying dermal connective tissue. Epithelial islands typically demonstrate palisading of the peripheral cells; frequently a clear zone of artifactual retraction is seen between the epithelial islands and the connective tissue (Fig.13).[1,8]
BCC. Tumor nests are composed of small, monotonous cells with dark nuclei and scant basophilic cytoplasm.
The treatment of basal cell carcinoma often depends on the size and site of the lesion. Small lesions (lesions < l cm) are treated by routine surgical excision, laser ablation or electrodesiccation and curettage (with 3- to 5 mm margins of clinically normal-appearing skin beyond the visible lesion). These methods result in a cure rate of 95% to 98%. Radical surgical excision and radiation therapy are recommended for large or aggressive lesions. For sclerosing types of BBC, recurrent lesions, or lesions situated near embryonic planes of fusion (along which these tumor cells tend to invade), a procedure called Mohs micrographic surgery should be used. This technique essentially uses frozen-section evaluation of specially mapped and marked surgical specimens to determine whether tumor tissue has been left behind. If it has, then the surgeon can return immediately to that particular area and remove more tissue, repeating the process until the patient is free of diseased margins.[1,8]
Verrucous carcinoma (VC) is a nonmetastasizing variant of well-differentiated squamous cell carcinoma (SCC) characterized by an exophytic, warty, slowly growing neoplasm with invading margins.[2,8]
Hoarseness is the most common presenting symptom; other symptoms include airway obstruction, weight loss, dysphagia, and throat pain. Enlarged lymph nodes are common and reactive rather than neoplastic (Fig. 14).[2,8]
Verrucous carcinoma wart-like appearance.
VC consists of thickened club-shaped papillae and blunt intrastromal invaginations of well-differentiated squamous epithelium with marked keratinization and thin fibrovascular cores. The squamous epithelium lacks cytologic criteria of malignancy, and by morphometry, the cells are larger than those seen in SCC. Mitoses are rare, and observed in the basal layers (Fig. 15).[2,8]
Verrucous carcinoma. A large lesion with abundant keratosis arranged in "church-spire" configuration. There is a broad, pushing border of infiltration.
Patients with VC may be treated by excision (by laser or surgery), or by radiotherapy. Although surgery is more effective, radiotherapy is an acceptable alternative for patients who are poor surgical candidates.
Malignant soft tissue tumors included here are Fibrosarcoma, Malignant fibrous histocytoma, Angiosarcoma, Rhabdomyosarcoma, Leiomyosarcoma, Kaposi sarcoma, Liposarcoma.
Presenting complaints are typically related to a nasal mass, obstruction or epistaxis, nasal discharge, pain or swelling in the facial region, or sensory changes involving the regional nerves. Radiographic studies typically documented a nasal or paranasal sinus mass with some associated bone erosion [12-14] This is also seen in the jaws.
Unlike the fibromatoses, fibrosarcomas are highly cellular proliferations. The spindle cells are often oriented in well-formed fascicle that frequently intersect at approximately 90 degree angles, creating a herringbone" pattern. Nuclear pleomorphism is usually not striking, but mitotic figures are often abundant, even in well-differentiated forms of the tumor. In the head and neck region, most fibrosarcomas are well-differentiated, low-grade neoplasms (Fig. 16).[1,8]
Low-grade fibrosarcoma consists of interlacing fascicles of spindle cells infiltrating around seromucinous glands.
The immunohistochemical reactivity of fibrosarcoma does not differ from that of aggressive fibromatosis. The neoplastic cells are often strongly reactive for vimentin and weakly reactive for actin. Negativity for epithelial markers (cytokeratin epithelial membrane antigen) and 8-100 protein is helpful in excluding differential diagnosis.[2,8]
Optimal treatment for aggressive fibromatosis is wide surgical resection. Unfortunately, this is often not an option in the head and neck region. Accordingly, the behavior in this location is more aggressive than in areas of easy resectability. In the head and neck, recurrence rates approach 60 to 70 percent excluding oral and paraoral lesions which are more amenable to surgery and have a recurrence rate of approximately 25 %. [2,8]
Patients may have nasal obstruction, often associated with epistaxis while pain, sinusitis, nasal discharge, swelling, anosmia, and proptosis are less common. Malignant fibrous histiocytoma (MFH) is currently used as a diagnosis of exclusion for sarcomas. Only 3% of MFH occur in the head and neck, with 30% of these arising in the sinonasal area.[2,8]
Sinonasal MFH are generally infiltrative and ulcerative, but can occasionally be circumscribed. Pleomorphic MFH, the most frequent morphologic subtype of MFH in the sinonasal tract, is characterized by spindle to pleomorphic cells in a storiform growth pattern, with easily identified mitotic figures including atypical forms, and necrosis. The cells are fusiform with, indistinct cytoplasm. Tumoral giant cells with multiple nuclei may be found (Fig. 17).[1,2,8]
Malignant fibrous histocytoma showing spindle-shaped cells with storiform pattern.
MFH is usually positive for vimentin and focally for actins. Importantly, MFH is a diagnosis of exclusion and is generally negative for desmin, skeletal muscle specific markers, S100 protein, HMB-45, epithelial markers and lymphoid markers.[2,8]
Compared with other anatomical sites, MFHs of the head and neck generally have a slightly lower rate of recurrence and metastases.[15]
Angiosarcoma is a malignant neoplasm of vascular phenotype whose constituent tumor cells have endothelial features.
Presenting symptoms include swelling, pain, epistaxis, deviation or swelling of tonsils, nasal obstruction, and sinusitis. [16,17]
Most sinonasal angiosarcomas are histologically low-grade. They infiltrate the adjacent tissues and bone, accompanied by necrosis and hemorrhage. They are comprised of tortuous anastomosing vascular channels that dissect the stroma, capillary sized vessels and cavernous vascular spaces. The lining endothelial cells range from flat to plump spindly to epithelioid, and often form papillary tufts (Fig. 18). [1- 8]
Angiosarcoma shows large vessel like spaces partially lined by enlarged, hyperchromatic endothelial cells.
Angiosarcomas are immunoreactive for CD34, CD31, Factor VIII R-Ag and vimentin, and focally keratin (especially the epithelioid variant) and actin [18]
Patients are usually treated by surgical resection with radiation and/or chemotherapy. Recurrences are common (50%), likely due to incomplete excision or possible multifocality. Metastasis is uncommon, and the predilection sites are the lung, liver, spleen, and bone marrow. [1,2,4,5,7,8,19]
Rhabdomyosarcoma primarily occurs during the first decade of life but also may occur in teenagers and young adults. It is rare in people older than 45 years, and approximately 60% of all cases occur in males. Embryonal rhabdomyosarcomas are most common in the first 10 years of life and account for about 60% of all cases. Alveolar rhabdomyosarcomas occur most often in persons between 10 and 25 years of age: they account for 20% to 30% of all tumors. Pleomorphic rhabdomyosarcomas represent less than 5% of all cases and show a peak prevalence in patients older than 40 years of age. The tumor is most often a painless, infiltrative mass that may grow rapidly. In the head and neck region the face and orbit are the most frequent locations followed by the nasal cavity. The palate is the most frequent intraoral site, and some lesions may appear to arise in the maxillary sinus and break through into the oral cavity[1- 8]
Several microscopic patterns of pediatric rhabdomyosarcoma are recognized including: Embryonal rhabdomyosarcoma, Non Otherwise Specified, Botryoid, Spindle, Alveolar rhabdomyosarcoma, Undifferentiated sarcoma and Anaplastic rhabdomyosarcoma. The anaplastic cells vary according to type (Fig.19).
A. Embryonal rhabdomyosarcoma. B. Alveolar subtype of rhabdomyosarcoma.
There is immunoreactivity for desmin, muscle specific actin, myoglobin, fast myosin, nuclear MyoD1 and nuclear myogenin (skeletal muscle myogenin myf4). CD99 may be positive in 16% of cases [20,21].
Before 1960 the prognosis for a patient with rhabdomyosarcoma was extremely poor, with more than 90% of patients dying. With the advent of multimodal therapy during the past several decades, the prognosis has improved dramatically. Treatment typically consists of local surgical excision followed by multiagent chemotherapy (vincristine actinomycin D. and cyclophosphamide). Postoperative radiation therapy also is used, except for localized tumors that have been completely resected at initial surgery. The 5-year survival rate for embryonal rhabdomyo sarcoma not otherwise specified [NOS]) is around 66%, although the figures for botryoid (95%) and spindle cell variants (88%) are much better. The 5-year survival rate for alveolar rhabdomyosarcoma is only 53%. and survival drops to slightly less than 50% for anaplastic rhabdomyosarcoma and undifferentiated sarcomas. [1-8]
Leiomyosarcoma is a malignant tumor of smooth muscle phenotype.
Patients may have swelling, pain and the duration of symptoms is usually long. There is usually no lymphadenopathy. Plain radiographs show opacification of the nasal cavity or sinus(es), often suggesting sinusitis Only a small number of sinonasal leiomyosarcomas have been reported, accounting for <1% of all non-epithelial tumors. They occur in all ages, with a peak in the 6th decade (mean, 53 years) without a gender difference. [2,22]
Leiomyosarcomas are infiltrative neoplasms accompanied by surface ulceration Bone or cartilage invasion is more frequent than surface or seromucinous gland invasion. Leiomyosarcomas are composed of right-angle intersecting bundles of spindle cells. Pallisading storiform and “haemangiopericytoma -like” patterns can occur. The tumors are hypercellular, but coagulative tumor necrosis and hemorrhage can create a hypocellular appearance. The tumor cells have elongated, vesicular to hyperchromatic, lobulated or indented nuclei with blunt ends (“cigar shaped”). The cytoplasm is fibrillary and eosinophilic, with frequent perinuclear vacuolation. Mitoses, both typical and atypical, are present to a variable degree. [2,22] Histochemistry and immunoprofile intracytoplasmic glycogen can be demonstrated with a PAS stain. Masson trichrome stain demonstrates red, longitudinally oriented parallel fibrils within the cytoplasm. Tumor cells are diffusely and strongly immunoreactive for vimentin, actin(smooth muscle or muscle- specific), desmin and h-caldesmon.There is generally no reactivity with keratin CD34, CD117, S-100 protein or HMB-45 The Ki-67 index is usually >15% (Fig. 20).[2,3,22]
Leiomyosarcoma fascicles of spindle-shaped cells with conspicuous eosinophilic cytoplasm.
About half of the reported cases develop local recurrence, often within a year and nearly 1/3 of these patients subsequently develop metastasis (mostly to the lungs and liver). Complete surgical excision is difficult to achieve, and radiation and chemotherapy are used with variable success. Poor prognostic factors include involvement of more than one contiguous site, large tumor size (>5 cm), high mitotic count (>20/10 high power field), tumor necrosis, and tumor stage. [2,22,23]
Kaposi sarcoma (KS) is a locally aggressive tumor that typically presents with cutaneous lesions in the form of multiple patches, plaques or nodules but may also involve mucosal sites, lymph nodes and visceral organs. The disease is uniformly associated with HIV and human herpes virus 8 (HHV-8) infection.[2,8]
KS is characterized by the appearance of purplish, reddish blue or dark brown macules, plaques and nodules that may ulcerate. They are particularly frequent in distal extremities and may be accompanied by lymphedema. Early oral KS is represented by solitary or multiple red or bluish flat lesions, while the later stage is characterized by a nodular, sometimes massive appearance with or without secondary ulceration (Fig. 21). [2,8]
Kaposi sarcoma of the palate.
KS lesions of the skin or the mucosa are uncharacteristic and present with subtle vascular proliferation; vascular spaces are increased in number, of irregular shape, and may dissect collagen fibres in the superficial corium. They often run parallel to the epithelium. The vascular proliferation is often perivascular and periadnexal. Endothelial cells lining the spaces are flattened or more oval, with little atypia. Preexisting blood vessels may protrude into the lumen of new vessels. Admixed are sparse lymphocytes and plasma cells; frequently, extravasated erythrocytes and deposits of hemosiderin surround the vascular structures (Fig. 22). [2,8]
Vascular slits and sparsely distributed lymphocytes of KS.
The lining cells of clearly developed vascular structures are usually positive for vascular markers, while the spindle cells consistently show positive reaction for CD34 and commonly for CD31 but are factor VIII negative. All cases, irrespective of epidemiologic subgroup, are HHV-8 positive. The new marker FLI1, a nuclear transcription factor, appears to be expressed in almost 100% of different vascular tumors, including KS [24]
The evolution of disease depends on the epidemiological-clinical type of KS and on its clinical extent. It is also modified by treatment that includes surgery, radio and chemotherapy. [25]
Liposarcomas are primarily seen in adults, with peak prevalence between the ages of 40 and 60. The tumor is typically a soft, slow-growing, ill-defined mass that may appear normal in color or yellow. Pain or tenderness is uncommon: when present, it is usually a late feature. The neck is the most common site for liposarcomas of the head and neck region. The most frequent oral locations are the tongue and cheek.[1,8]
Most liposarcomas can be divided into three major categories: 1. Well-differentiated liposarcoma/atypical lipomatous tumor, 2. Myxoid/round cell liposarcoma, 3. Pleomorphic liposarcoma(Fig.23). [1,8]
Liposarcoma showing lipoblasts interspersed between mature appearing adipocytes.
Benign and malignant odogentic tumors included here are the Calcifying epithelial odontogenic tumor (CEOT), Ameloblastic fibroma (AF), Cementoblastoma, Odontoma, Odontogenic myxoma, Ameloblastoma, Ameloblastic carcinoma and Adenomatoid odontogenic tumor.
CEOT accounts for approximately 1% of all odontogenic tumors occurring in patients between 20 and 60 years of age, with a mean age of 40 years. There is no gender predilection. Most cases are intraosseous, approximately 6% arise in extraosseous locations. Intraosseous tumors affect the mandible more often than the maxilla with a ratio of 2:1.[2,8]
The tumor presents as an asymptomatic slow-growing expansile mass of the jaw. Peripheral gingival lesions are firm painless masses. Radiographically, most CEOTs present as mixed radiolucent-radiopaque lesions, but they may show considerable variation. They may be unilocular or multilocular. In about half of the cases, an unerupted tooth, most often a mandibular third molar, is associated with the lesion. CT and MRI provide useful information in the diagnosis and treatment of CEOT [26]
The tumor consists of a fibrous stroma with islands and sheets of polyhedral epithelial cells with abundant eosinophilic cytoplasm, sharply defined cell borders and well-developed intercellular bridges. Their nuclei are frequently pleomorphic, with giant nuclei being common. Mitotic figures are rarely encountered unless malignant transformation occurs (Fig.24).[27]
CEOT depicting fibrous stroma with islands and sheets of polyhedral epithelial cells with abundant eosinophilic cytoplasm.
Most cases of AF present as a painless swelling or are discovered due to disturbances of tooth eruption. Radiographically, the tumor presents as a well-demarcated radiolucency, often in connection with a malpositioned tooth (Fig.25).[30]
AF presenting as well demarcated osteolysis with sclerotic rim.
The epithelial component of AF consists of branching and anastomosing epithelial strands that form knots of varying size. These have a peripheral rim of columnar cells similar to the inner enamel epithelium that embraces a loosely arranged spindle-shaped epithelium identical to stellate reticulum.The epithelial component resembles ameloblastoma. The stromal component however differs in that it is an immature cell-rich myxoid tissue with an embryonic appearance. Some AFs may contain granular cells (Fig.26). [30]
Ameloblastic fibroma with strands and islands of odontogenic epithelium showing peripheral palisading, embedded in a cell-rich ectomesenchyme resembling the dental papilla.
Treatment consists of enucleation and curettage. Recurrence may occur but this does not justify initial aggressive treatment.[30] Rarely, AF may progress to malignancy (ameloblastic fibrosarcoma).
Cementoblastoma is a rare benign neoplasm which forms cementum-like material attached to the tooth root.
Cementoblastomas are rare, accounting for only about 4% of cementum-containing lesions. There is no significant gender predilection and lesions are discovered in the 2nd-3rd decades. Lesions present with varied levels of pain and a swelling of the buccal or lingual aspect of the alveolar ridge as a result of bone expansion. The involved tooth usually remains vital. There is a predilection for the mandibular, particularly the mandibular permanent first molar.[5,8]
The tumor is well-defined, radiopaque or mixed density, round mass, intimately associated with the tooth root. Additionally, a thin radiolucent rim surrounds the tumor, representing the periodontal ligament. Root resorption is common. Irregular soft tissue may surround the lesion (Fig. 27). [5,8]
Radiograph of a radiodense calcified mass attached to the root of the mandibular first molar is characteristic for a cementoblastoma.
Cementoblastoma is composed of a dense mass of cementum in a loose fibrovascular stroma. Lesions usually show prominent cementoblastic rimming and may demonstrate a characteristic basophilic appearance and reversal lines of the cementum. Multinucleated osteoclastic giant cells are usually present. The periphery may have radiating columns of unmineralized tissue (Fig. 28). [5,8]
Cementoblastoma. Mineralized tissue containing numerous plump cementoblasts.
Odontoma is the most common odontogenic tumor, although it may best be classified as a hamartoma composed of enamel, dentin, pulpal tissue, and cementum. Academically, odontomas are subclassified into two types, although management is identical: compound when composed of rudimentary teeth-like structures and complex when composed of haphazardly arranged tooth structure. [5,8]
Odontoma occurs more frequently than all other odontogenic tumors combined. Odontomas show no gender predilection. Odontomas develop most commonly in the first two decades, the time normal teeth are developing and erupting. Most odontomas are asymptomatic, found incidentally on routine dental radiographs, while larger lesions may interfere with eruption of normal adjacent teeth, prompting radiographic investigation. [5,8]
Odontomas present as a radiodense calcified mass surrounded by a thin radiolucent rim. Compound odontomas will appear like small, malformed teeth while complex odontomas present as radiodense masses of calcified tooth material, slightly more difficult to diagnose[5,8]
Sections of immature, developing compound odontomas show several dysmorphic tooth germs in a loosely textured connective tissue with cords and islands of odontogenic epithelium. Much of the enamel matrix is preserved in spite of decalcification The distinction between complex and compound odontoma is mainly based on the presence of tooth- like structures in compound odontomas (Fig. 29). [5,8]
A. Compound odontoma. Enamel matrix and odontogenic epithelium in an odontoma. B. Odontoma, complex type. Enamel, dentin, and cementum-like tissue are arranged in a haphazard pattern.
Small OMs are asymptomatic. Large OMs cause painless expansion. Cortical perforation may occur when large. Unilateral sinonasal obliteration may mimic nasal polyposis. Radiographically, OM appears as a unilocular or multilocular radiolucency, sometimes showing a fine “soap bubble” or“honeycomb” appearance occasionally with fine trabeculations. The borders of the tumor are usually well-defined and corticated but can be poorly defined or diffuse. Root displacement occurs, as does root resorption. Larger OMs may present with periosteal reactions. CT may reveal the fine bony septa and allows for anatomic deliniation.[1,2,31]
OM is characterized by randomly oriented stellate, spindle-shaped and round cells with long, fine, anastomosing pale or slightly eosinophilic cytoplasmic processes extending from the centrally placed nucleus. Cells are evenly dispersed in an abundant mucoid or myxoid stroma that contains only a few fine collagen fibres. Binucleated cells, mild pleomorphism and mitotic figures may occur. Rests of odontogenic epithelium are not obvious in most lesions and are not required for establishing final diagnosis. Some OMs may permeate into the marrow spaces in a pseudo-malignant pattern. Some OMs have a tendency to produce collagen fibres and are designated myxofibroma. There is no evidence that these more collagenous variants behave differently. Histochemical studies show that the ground substance is rich in acid mucopolysaccharides, primarily hyaluronic acid and, to a lesser degree, chondroitin sulphate (Fig.30).[1,2,32]
Odontogenic myxoma with randomly oriented stellate, spindle-shaped and round cells with long cytoplasmic processes.
The tendency of OM to permeate into marrow spaces makes effective enucleation and curettage difficult. Small lesions have been successfully treated in this way but larger lesions may require complete excision with free margins. Recurrence rates from various studies average about 25% but in spite of this, the prognosis is good. Recurrence usually follows incomplete removal within 2 years but may also occur later. Death may ensue due to cranial base extension.[1-3,33]
Ameloblastoma occurs exclusively in the jaws, rarely in the sinonasal cavities. Most maxillary cases occur in the posterior region. Small lesions may be asymptomatic swellings of the jaws. Pain or paraesthesia is rare. They may be unilocular or multilocular radiolucencies resembling cysts and they may reveal scalloped borders [1,2,34]. The most typical radiographic feature is that of a multilocular radiolucent lesion. The lesion is often described as having a "soap bubble" appearance (when the radiolucent loculations are large) or as being "honeycombed"(when the loculations are small). Buccal and lingual cortical expansion is frequently present. Resorption of the roots of teeth adjacent to the tumor is common. In many cases an unerupted tooth, most often a mandibular third molar is associated with the radiolucent defect. Solid ameloblastomas may radiographically appear as unilocular radiolucent defects, which may resemble almost any type of cystic lesion (Fig. 31). [1-5]
Ameloblastoma involved maxillary sinus.
The follicular and plexiform patterns are the most common. Less common histopathologic patterns include the acanthomatous, granular cell, desmoplastic, and basal cell types (Fig. 32).[1-3, 8]
Follicular ameloblastoma
Patients with conventional solid or multicystic intraosseous ameloblastomas have been treated by a variety of means. These range from simple enucleation and curettage to en bloc resection. Other surgeons advocate that the margin of the resection should be at least 1.0 to 1.5 cm past the radiographic limits of the tumor. Ameloblastomas of the posterior maxilla are particularly dangerous because of the difficulty of obtaining an adequate surgical margin around the tumor. Marginal resection is the most widely used treatment but recurrence rates of up to 15% have been reported after marginal or block resection.[1,2,8]
Only 19 cases have been reported to occur in the maxilla. Males and females are equally affected. The posterior segments of the jaws represent the most common site. Generally, ill defined or irregularly marginated radiolucencies are characteristic. Cortical expansion often with perforation, may be present as well as infiltration into adjacent structures (Fig. 33).[2,35]
Ameloblastic carcinoma in maxillary sinus
Ameloblastic carcinoma is characterized by malignant cytologic features in combination with the overall histological pattern of an ameloblastoma. A tall columnar cellular morphology with pleomorphism mitotic activity, focal necrosis, perineural invasion and nuclear hyperchromatism may be present. Peripheral palisading and so-called reverse or inverted nuclear polarity will be present. A stellate reticulum structure will usually be seen. Cystic spaces may be present that are lined by epithelium Atypical cells form nests and broad ribbons which may branch and anastomose with focal areas of subtle necrosis to more obvious central, comedo necrosis like areas (Fig. 34).[1,2,36]
Ameloblastic Carcinoma. A tall columnar cellular morphology with pleomorphism mitotic activity
Intraosseous AOTs may be found in association with unerupted permanent teeth (follicular type), in particular the four canines that account for 60% with the maxillary canines alone accounting for 40%. Most AOTs are asymptomatic. When growth of the intraosseous variants causes cortical expansion, it may present as a palpable bony-hard swelling with or without slight pain. The intraosseous AOTs may cause displacement of neighbouring teeth. The peripheral variant presents as a fibroma or an epulis-like lesion of the gingiva Radiographically, the intraosseous, follicular AOT, shows a well-defined, unilocular radiolucency around the crown and often part of the root of an unerupted permanent tooth, mimicking a dentigerous cyst. If not associated with an unerupted tooth (extrafollicular type), AOT presents as a unilocular radiolucent lesion. In two thirds of the intraosseous variant, the radiolucency shows discrete radiopaque foci. The peripheral variant may disclose erosion (saucerization) of the alveolar bone crest.(Fig.35).[1,2,8]
AOT involving the maxillary sinus.
Microscopically, the tumor is composed of spindle shaped epithelial cells that form sheets, strands, or whorled masses of cells in a scant fibrous stroma. The epithelial cells may form rosette-like structures about a central space, which may be empty or contain small amounts of eosinophilic material. This material may stain for amyloid. The tubular or ductlike structures, which are the characteristic feature of the adenomatoid odontogenic tumor, may be prominent, scanty, or even absent in a given lesion. These consist of a central space surrounded by a layer of columnar or cuboidal epithelial cells. The nuclei of these cells tend to be polarized away from the central space. The mechanism of formation of these tubular structures is not entirely clear but is likely the result of the secretory activity of the tumor cells, which appear to be preameloblasts. In any event, these structures are not true ducts, and no glandular elements are present. Small foci of calcification may also be scattered throughout the tumor (Fig. 36).[1,2]
AOT. Solid, cell-rich area of minimal stromal connective tissue showing duct-like structures.
These include: Hodgkins, Burkitt’s lymphoma, Plasmacytoma (multiple myeloma) and Non-Hodgkins lymphoma.
Hodgkin\'s lymphoma almost always begins in the lymph nodes, and any lymph node group is susceptible. Oral involvement has been reported, but it is rare. In about 30% of patients with Hodgkin\'s disease, other systemic signs and symptoms may be present, such as weight loss, fever, night sweats, and generalized pruritus (itching).[1,8]
Hodgkin\'s lymphoma is recognized to comprise two main forms. [1] Nodular Ivmphocyte-predominant Hodgkin\'s lymphoma and [2] Classic Hodgkin\'s lymphoma, the latter of which is divided into five subtypes. Although this group of diseases has certain features in common, current immunohistochemical and molecular biologic techniques have allowed distinctions to be made among the various types. The common features include effacement of the normal nodal architecture by a diffuse, often mixed, infiltrate of inflammatory cells that is interspersed with large, atypical neoplastic lymphoid cells. In the case of classical Hodgkin\'s lymphoma, this atypical cell is known as a Reed- Sternberg cell (Fig. 37). [1,8]
Hodgkin\'s lymphoma. This high-power photomicrograph shows the characteristic Reed-Sternberg cell.
The treatment of Hodgkin\'s lymphoma depends on the stage of involvement. Patients who had limited disease often were managed by local radiation therapy alone. Recent treatment trends, however, combine less extensive radiotherapy fields with milder multiagent chemotherapy regimens to maximize disease control and minimize long-term complications of therapy. [1,8]
Burkitt\'s lymphoma is a malignancy of B-lymphocyte origin that represents an undifferentiated lymphoma[1,8]
As many as 50% to 70% of the cases of endemic Burkitt\'s lymphoma present in the jaws. The malignancy usually affects children (peak prevalence, about 7 years of age) who live in Central Africa, and a male predilection is usually reported. The posterior segments of the jaws are more commonly affected, and the maxilla is involved more commonly than the mandible (a 2:1 ratio). Sometimes all four quadrants of the jaws show tumor involvement. The tendency for jaw involvement seems to be age related; nearly 90% of 3 year-old patients have jaw lesions, in contrast to only 25% of patients older than age 15. Sporadic Burkitt\'s lymphoma tends to affect patients over a greater age range than is noted for the African tumor. Although the abdominal region is typically affected, jaw lesions have been reported in sporadic cases.[1,8] The growth of the tumor mass may produce facial swelling and proptosis. Pain, tenderness, and paresthesia are usually minimal, although marked tooth mobility may be present because of the aggressive destruction of the alveolar bone. Premature exfoliation of deciduous teeth and enlargement of the gingiva or alveolar process may also be seen. The radiographic features are consistent with a malignant process and include a radiolucent destruction of the bone with ragged, ill-defined margins. [1,8]
Burkitt\'s lymphoma histopathologically represents an undifferentiated, small, noncleaved B-cell lymphoma. The lesion has broad sheets of tumor cells that exhibit round nuclei with minimal cytoplasm. Each tumor nucleus often has several prominent nucleoli and numerous mitotic cells. Immunohistochemical studies using markers identify proliferating cells (e.g. Ki-67) typically show that almost 100% of the tumor cells are in the process of replicating. On viewing the lesion on low-power magnification, a classic "starry-sky" pattern is seen (Fig. 38) [1,8]
Burkitt\'s lymphoma "starry-sky" appearance, a pattern caused by interspersed histiocytic cells with abundant cytoplasm
Burkitt\'s lymphoma is an aggressive malignancy that usually results in the death of the patient within 4 to 6 months after diagnosis if it is not treated. Treatment generally consists of an intensive chemotherapeutic regimen, which emphasizes the use of high doses of cyclophosphamide. More than 90% of the patients respond to this treatment. The prognosis for Burkitt\'s lymphoma in the past was poor, with a median survival time of only months.
The plasmacytoma is a unifocal, monoclonal, neoplastic proliferation of plasma cells that usually arises within bone. [1- 8]
The plasmacytoma usually is detected in an adult male, with an average age at diagnosis of 55 years. The male-to-female ratio is 3:1. Most of the lesions present centrally within a single bone.
Approximately 80% to 90% of extramedullary plasmacytomas develop in the head and neck region, and such lesions have been reported in the tonsils, nasopharynx, and paranasal sinuses.[1-8]
The histopathologic features of the plasmacytoma are identical to those of multiple myeloma. Sheets of plasma cells show varying degrees of differentiation. Immunohistochemical studies demonstrate that these plasma cells are monoclonal. As many as 25% to 50% of these patients also show a monoclonal gammopathy on evaluation by serum protein immunoelectrophoresis (Fig. 39).[1-8]
Plasmacytoma. Sheets of monomorphous-appearing plasma cells
Immunohistochemically, the plasma cells express cytoplasmic immunoglobulin with light chain restriction. CD20 is negative in most cases, and some cases express CD79a. PAX-5 is negative, while Oct-2 and Bob.1 are frequently positive. There is usually expression of CD38, CD138 and VS38, markers characteristically positive in but not specific for plasma cells.Epithelial membrane antigen is commonly positive, and rare cases can show cytokeratin immunoreactivity (often with a dot pattern). Leukocyte common antigen, CD31 or CD56 is sometimes positive. [1-8]
Plasmacytomas are usually treated with radiation therapy, and typically a dose of at least 4000 cGy is delivered to the tumor site. A few lesions have been surgically excised with good results, although this is not the preferred treatment in most instances. Unfortunately, when patients with plasmacytoma of bone are observed on a long-term basis, most will eventually develop multiple myeloma. [1-8]
Lymphomas of the paranasal sinuses commonly show bony destruction and local extension to adjacent structures including the orbit, palate, nasal cavity, nasopharynx, and soft tissues in the cheek and infratemporal fossa. The maxillary sinus is the most commonly involved paranasal sinus. Patients may present with nasal obstruction, epistaxis, nasal discharge, pain and nasal swelling or facial swelling. Locally advanced cases can cause destruction of midline facial structures. The nasal septum or palate may be perforated. Extension to the orbits can lead to proptosis and visual disturbance. Regional lymph node involvement may occur in some patients. Occasional patients have systemic symptoms including fever and weight loss. Hemophagocytic syndrome with pancytopenia occurs at presentation in a minority of patients with extranodal NK/T cell lymphoma of nasal type. [1-8, 38]Lymphoma in patients with AIDS usually occurs in extranodal locations, with the CNS being the most common site. Oral lesions are seen in approximately 4% of patients with AIDS-related NHL and most frequently involve the gingiva, palate, tongue, tonsil, or maxillary sinus (Fig. 40). [1-8]
Non-hodgkins lymphoma with destruction in the left maxillary sinus.
Non-hodgkins lymphoma consists of several subtypes: Diffuse small cleaved cell, Diffuse mixed small and large cell, Diffuse large cell, Diffuse large cell immunoblastic, Follicular large cell, Small noncleaved cell, Lymphoblastic, Follicular mixed small and large cell, Small lymphocytic and Follicular small cleaved cell variants.
Non-Hodgkins lymphoma; Diffuse small cell lymphoma.
The lymphoma most commonly exhibits an NK-cell immunophenotype of CD2+, surface CD3(Leu4)-, cytoplasmic CD3+, CD56+. CD43 and CD45RO are commonly positive, but other T-cell markers (including CD5) and NK-cell markers (CD16, CD57) are usually negative[1-8,39]
Radiotherapy and/or systemic chemotherapy is the treatment of choice for localized disease. Treatment of DLBCL follow protocols for similar tumors elsewhere in the body, as some series showed that chemotherapy might be beneficial. The overall survival for extranodal NK/T cell lymphoma of nasal-type is only 30-50%. In patients achieving complete remission, local relapse occurs in one-third to one-half of cases, and systemic failure is also common. Factors associated with a worse outcome include: Advanced stage, poor systemic status and severe disease.There is no conclusive evidence to suggest that the histological grading of NK/T cell lymphoma can predict the clinical outcome. Expression of cutaneous lymphocyte antigen (CLA) may be associated with a worse prognosis, but this finding has yet to be confirmed. [1-8]
Cherubism, Paget’s Disease, Osteoid osteoma, Osteoma, Juvenile ossifying fibroma, Fibrous dysplasia, Giant cell tumor (central and peripheral), Chondrocarcoma, Osteosarcoma and Ewing’s sarcoma are common bone tumors discussed herein.
Cherubism is a rare, autosomal dominant inherited disease that causes bilateral swelling of at least the mandible but often also the maxilla. [1,5,8]
Males are affected more commonly than females and most patients present in early childhood. There is often a history of other afflicted family members. The resulting painless, symmetrical, facial deformity mimics the angelic faces of the cherubs portrayed in Renaissance and Baroque paintings, hence its name. Sometimes there is upward displacement of both eyes. The disease progression is self-limited, stabilizing at the end of puberty. Complications developing from the jaw disorder can result in poor dentition, impacted teeth, and malaligned teeth. [1,5,8]
Radiographic findings are not pathognomonic, but the presence of bilateral, usually symmetrical involvement of the maxilla and mandible is certainly most suggested. The affected jaw areas show cortical expansion and attenuation (thinning) as well as a soap bubble-like multilocular radiolucency. Teeth and tooth germs may be displaced (Fig.42).[1,5,8]
Bilateral soap bubble-like radiolucencies with displaced teeth and tooth germs in cherubism.
Cherubism shows multinucleated, osteoclast-like giant cells lying in a fibroblastic background stroma. The fibroblastic tissue may vary in cellularity from very dense to cell-poor. Mitotic figures may be encountered but are usually not numerous and not atypical. The giant cells mostly cluster in areas of hemorrhage, but they also may lie more dispersed among the lesion. Bone formation is usually confined to the periphery of the lesion, as a reactive remodeling.There may also be a component consisting of immature odontogenic tissue due to developing tooth germs lying within the lesional tissue (Fig.43). [1,5,8]
Histologically cherubism shows moderately cellular fibroblastic tissue with dispersed osteoclast-like giant cells and some extravasation of erythrocytes.
With the onset of puberty, the lesions may lose their activity and may mature to fibrous tissue and bone. Facial deformity may necessitate cosmetic surgery.
Paget\'s disease of bone is a condition characterized by abnormal and anarchic resorption and deposition of bone, resulting in distortion and weakening of the affected bones. The cause of Paget\'s disease is unknown, but inflammatory, genetic, and endocrine factors may be contributing agents. In some studies 15% to 40% of affected patients have a positive family history of the disease. In recent years, recurrent mutations in the sequestosome 1 gene (SQSTA11, also known as p62) which participates in the regulation of osteoclastic activity via the nuclear factor-KB (NF-KB) transcription activation pathway, have been identified in both familial and sporadic cases of the disease. [1,8]
Jaw involvement is present in approximately 17% of patients diagnosed with Paget\'s disease. Maxillary disease, which is far more common than mandibular involvement, results in enlargement of the middle third of the face. In extreme cases, the alteration results in a lion-like facial deformity (leontiasis ossea). Nasal obstruction, enlarged turbinates, obliterated sinuses, and deviated septum may develop secondary to maxillary involvement. The alveolar ridges tend to remain symmetrical but become grossly enlarged. If the patient is dentulous then the enlargement causes spacing of the teeth. Edentulous patients may complain that their dentures no longer fit because of the increased alveolar size. Radiographically, the early stages of Paget\'s disease reveal a decreased radiodensity of the bone and alteration of the trabecular pattern. Particularly in the skull, large circumscribed areas of radiolucency may be present (osteoporosis circumscripta (Fig.44).[1,8]
Paget\'s disease. Periapical film showing the "cotton wool" appearance of the bone.
Microscopic examination shows an apparent uncontrolled alternating resorption and formation of bone. In the active resorptive stages, numerous osteoclasts surround bone trabeculae and show evidence of resorptive activity. Simultaneously, osteoblastic activity is seen with formation of osteoid rims around bone trabeculae. A highly vascular fibrous connective tissue replaces the marrow. A characteristic microscopic feature is the presence of basophilic reversal lines in the bone. These lines indicate the junction between alternating resorptive and formative phases of the bone and result in a "jigsaw puzzle." or "mosaic," appearance of the bone (Fig.45). [1,8]
Paget\'s disease. Osteoblastic and osteoclastic activity surround the bone trabeculae.
Osteoid osteoma is a benign bone-forming tumor of limited growth potential, usually less than 1.5 cm, typically associated with nocturnal pain that is relieved by salicylates. It is very rare in the head and neck. It occurs in young patients (first three decades), with male predominance. On plain radiographs, dense cortical sclerosis surrounds a radiolucent nidus. Histologically, the nidus shows interconnected, ossified woven bone rimmed by osteoblasts. Fibrous tissue, vessels and multinucleated giant cells are identified inbetween the bony trabeculae (Fig.46).[1,2,8]
Osteoid osteoma. Osteoblasts surround the trabeculae.
Osteomas are benign tumors composed of mature compact or cancellous bone. Osteomas are essentially restricted to the craniofacial skeleton and rarely symptomatic. Although pain, swelling, sinusitis, and nasal discharge are possible. In rare cases, paranasal sinus osteomas may expand into orbital structures and result in proptosis, diplopia, and decreased visual acuity. [1-8] Osteomas of the jaws may arise on the surface of the bone, as a polvpoid or sessile mass (periosteal, peripheral or exophytic osteoma). Or they may be located in the medullary bone (endosteal or central osteoma). Extraskeletal lesions of soft tissue, typically located within muscle or the dermis of the skin (osteoma cutis), also are possible. Most jaw osteomas are detected in young adults and are generally asymptomatic. Paranasal sinus lesions also are possible and are actually more common than gnathic lesions. The frontal sinus is most commonly involved, followed by the ethmoid and maxillary sinuses. [1-8] Radiographically. osteomas appear as circumscribed sclerotic masses. Periosteal osteomas may show a uniform sclerotic pattern or may demonstrate a sclerotic periphery with a central trabecular pattern. Smaller endosteal osteomas are difficult, if not impossible, to differentiate from foci of sclerotic bone representing the end stage of an inflammatory process (condensing osteitis, focal chronic sclerosing osteomyelitis) or from noninflammatory foci of sclerotic bone (idiopathic osteosclerosis). The true nature of these osteomas can be confirmed only by documentation of continued growth (Fig.47). [1-8]
Osteoma in left side of maxilla.
A well-circumscribed nodule of mature dense bone is the characteristic feature.Bony trabeculae sometimes are rimmed by osteoblasts. Between bony trabeculae there may be fibrous tissue or fatty stroma with varying amounts of hematopoietic elements. Occasionally there are foci of mature cartilage (Fig.480.[1,8]
Osteoma. Trabeculae of lamellar bone with an intervening bland fibrous stroma.
Paranasal sinus osteomas may not require removal unless they become large or symptomatic; small, periosteal lesions may be removed endoscopically. Whereas larger lesions typically require an open surgical approach. Osteomas are completely benign, and patients do not experience malignant change. Recurrence after excision is extremely rare.[1- 8]
Although the two forms demonstrate different histopathologic and clinical features, several investigators have chosen to compromise and accept two patterns of juvenile ossifying fibroma: [1] trabecular and [2] psammomatoid.[1- 8]
In most instances, the neoplasms often grow rapidly, are well-circumscribed, and lack continuity with the adjacent normal bone. The lesions are circumscribed radiolucencies that in some cases contain central radiopacities. In some cases "ground glass" opacification may be observed. The age at diagnosis varies, with reported cases occurring in patients from younger than 6 months to older than 70 years of age. Lesions arising in the paranasal sinuses penetrate the orbital, nasal, and cranial cavities. Nasal obstruction, exophthalmos. or proptosis may be seen. Rarely, temporary or permanent blindness occurs in maxillary lesions exhibiting aggressive behavior (Fig.49).[1-8]
CT of Juvenile ossifying fibroma in left maxillary sinus.
Both patterns are typically nonencapsulated but well demarcated from the surrounding bone. The tumor consists of cellular fibrous connective tissue that exhibits areas that are loose and other zones that are so cellular that the cytoplasm of individual cells is hard to discern because of nuclear crowding. Myxomatous foci are not rare and often are associated with pseudocystic degeneration. Mitotic figures can be found but are not numerous. Areas of hemorrhage and small clusters of multinucleated giant cells are usually seen (Fig.50).[1-8]
Juvenile ossifying fibroma bony trabeculae lined by a rim of osteoblasts
For smaller lesions, complete local excision or thorough curettage appears adequate. For some rapidly growing lesions, wider resection may be required. In contrast to the negligible recurrence rate seen in the common types of ossifying fibromas. Recurrence rates of 30% to 58% have been reported for juvenile ossifying fibromas. Malignant transformation has not been documented.[1-8]
Fibrous dysplasia is a developmental tumor-like condition that is characterized by replacement of normal bone by an excessive proliferation of cellular fibrous connective tissue intermixed with irregular bony trabeculae. Fibrous dysplasia is a sporadic condition that results from a postzygotic mutation in the GNAS1 (guanine nucleotide-binding protein, a-stimulating activity polypeptide 1] gene. Clinically, fibrous dysplasia may manifest as a localized process involving only one bone, as a condition involving multiple bones, or as multiple bone lesions in conjunction with cutaneous and endocrine abnormalities (Fig.51). [1 -8]
Clinical features of fibrous dysplasia
The disease is limited to a single bone. This type accounts for about 80% to 85% of all cases, with the jaws being among the most commonly affected sites. The chief radiographic feature is a fine "ground glass" opacification that results from superimposition of a myriad of poorly calcified bone trabeculae arranged in a disorganized pattern. When the maxilla is involved, the lesional tissue displaces the sinus floor superiorly and commonly obliterates the maxillary sinus. Imaging studies in cases with maxillary involvement may show increased density of the base of the skull involving the occiput, sphenoid, roof of the orbit, and frontal bones. This is the most characteristic radiographic feature of fibrous dysplasia of the skull (Fig.52). [1 -8]
Fibrous dysplasia of the maxilla.-ground glass appearance.
Involvement of two or more bones is termed polyostotic fibrous dysplasia. a relatively uncommon condition. The number of involved bones varies from a few to 75% of the entire skeleton. When seen with cafe au lait (coffee with milk) pigmentation, the process is termed Jaffe-Lichtenstein syndrome. Polyostotic fibrous dysplasia also may be combined with cafe au lait pigmentation and multiple endocrinopathies. such as sexual precocity, pituitary adenoma, or hyperthyroidism. This pattern is known as the McCune-Albright Syndrome.[1-8]
The prototypical appearance of fibrous dysplasia consists of irregularly shaped trabeculae of osteoid and woven bone diffusely embedded in a cellular fibrous tissue stroma (Fig.53).[1,2]
Fibrous dysplasia. Trabeculae of woven bone without osteoblastic rimming.
Clinical management of fibrous dysplasia of the jaws may present a major problem. Although smaller lesions, may be surgically treated in their entirety without too much difficulty, the diffuse nature and large size of many lesions particularly those of the maxilla, preclude removal without extensive surgery. In many cases, the disease tends to stabilize and stop enlarging when skeletal maturation is reached. Some lesions, however, continue to grow, although slowly, in adult patients. Some patients with minimal cosmetic or functional deformity may not require or desire surgical treatment. Cosmetic deformity with associated psychologic problems or functional deformity may dictate surgical shaving in the younger patient. Such a procedure usually entails surgical reduction of the lesion to an acceptable contour without attempts to remove the entire lesion. The cosmetic result is usually good, but regrowth may occur over time. [1 -8]
Molar and premolar areas are more often affected than the anterior parts or the ascending ramus. Involvement of the condyle or maxillary sinus is rare. Most cases present as asymptomatic incidental findings. Some, however, present with pain or paraesthesia, swellings or loosening of teeth. Nasal obstruction may occur. Central or peripheral giant cell lesions (GCL) are expansile, radiolucent and often multiloculated lesions, rarely mixed opacities, with scalloped and mostly well-defined but non-corticated borders. With increasing size, multilocularity is more often noticed (Fig. 54). [1,2,40]
Giant cell lesion with destruction of the maxillary sinus.
The lesion consists of spindle-shaped fibroblastic or myofibroblastic cells, loosely arranged in a fibrous, sometimes fibromyxoid, vascularized tissue hemosiderin deposits, macrophages with hemorrhagic areas, lymphocytes, granulocytes and, rarely, plasma cells. Especially in the hemorrhagic, areas, evenly dispersed or small clusters of osteoclast-like giant cells are found. In addition, traversing collagen bundles are present, often accompanied by metaplastic bone formation giving the lesion a somewhat lobular appearance (Fig. 55). [1,2,3,41]
Giant cell lesion; scattered multinucleated cells surrounded by a fibrous tissue stroma.
Histological findings are not predictive of biological behaviour. The treatment of GCL is careful enucleation. In case of recurrences, more extensive surgery should be considered. Administration of calcitonin (intranasal or subcutaneously), or glucocorticoids (intralesional) has proven effective in some cases. Also antiangiogenic therapy with interferon alpha has been successfully applied. [1,2,3]
Chondrosarcoma is a malignant tumor characterized by the formation of cartilage.
A painless mass or swelling is the most common presenting sign. This may be associated with separation or loosening of teeth. Chondrosarcoma may involve the alveolar portion of the maxilla, the maxillary sinus or the nasal septum. Radiographically, the tumor usually shows features suggestive of a malignancy, consisting of a radiolucent process with poorly defined borders. The radiolucent area often contains scattered and variable amounts of radiopaque foci, caused by calcification or ossification of the cartilage matrix. Some chondrosarcomas show extensive calcification and radiographically appear as a densely calcified mass with irregular peripheral margins. Penetration of the cortex can result in a sunburst pattern similar to that seen in some osteosarcomas. When occurring in the head and neck, chondrosarcomas arise most frequently in the maxilla.[1,2,5] Maxillary tumors involve primarily the maxillary sinuses and nasal cavity and are less confined as they quickly erode the thin maxillary bone walls. Early jaw symptoms frequently include malocclusion with developing diastemas, loose teeth and eventual bony destruction (Fig. 560. [1- 5]
Chondrosarcoma of the left maxilla
Chondrosarcomas are composed of cartilage showing varying degrees of maturation and cellularity. In most cases, typical lacunar formation within the chondroid matrix is visible, although this feature may be scarce in poorly differentiated tumors. The tumor often shows a lobular growth pattern, with tumor lobules separated by thin fibrous connective tissue septa (Fig. 57). [1- 5]
Chondrosarcoma. Cartilaginous neoplasm shows an abundant matrix that surrounds chondrocytes and mild nuclear irregularities.
The prognosis for chondrosarcoma is related to the size, location, and grade of the lesion. The most important factor is the location because this has the greatest influence on the ability to achieve complete resection. The most effective treatment for chondrosarcoma is radical surgical excision. Radiation and chemotherapy are less effective when compared with osteosarcoma and are primarily used for unresectable high-grade chondrosarcomas.[5,6] Chondrosarcomas are associated with an excellent prognosis if the lesions are completely resected. Approximately 20% of patients die of tumor, most often with uncontrolled local recurrence. Mesenchymal chondrosarcoma is a high-grade tumor with an unpredictable prognosis. Patients with tumor of the facial skeleton do better than those with tumors of the remainder of the skeleton[1,2,4- 6]
The maxilla and mandible are involved with about equal frequency. Mandibular tumors arise more frequently in the posterior body and horizontal ramus rather than the ascending ramus. Maxillary lesions are discovered more commonly in the inferior portion (alveolar ridge, sinus floor, palate) than the superior aspects (zygoma, orbital rim). Swelling and pain are the most common symptoms Loosening of teeth, paresthesia. and nasal obstruction (in the case of maxillary tumors) also may be noted. Some patients report symptoms for relatively long periods before diagnosis, which indicates that some rare osteosarcomas of the jaws grow rather slowly. The radiographic findings vary from dense sclerosis to a mixed sclerotic and radiolucent lesion to an entirely radiolucent process. The peripheral border of the lesion is usually ill-defined and indistinct, making it difficult to determine the extent of the tumor radiographically. In some cases, an extensive osteosarcoma may show only minimal or subtle radiographic change with only slight variation in the trabecular pattern. Occasionally, there is resorption of the roots of teeth involved by the tumor. This feature is often described as "spiking" resorption as a result of the tapered narrowing of the root. The "classic" sunburst or sun ray appearance caused by osteophytic bone production on the surface of the lesion is noted in about 25% of jaw osteosarcomas. Often this is appreciated best on an occlusal projection. In few cases a triangular elevation of the periosteum, referred to as Codman\'s triangle, may be observed (Fig. 58).[1,3,8]
A. CT scan of an osteosarcoma of the maxilla. B. Oral view.
Depending on the amount of osteoid, cartilage or collagen fibers produced by the tumor, many pathologists subclassify osteosarcomas into Osteoblastic, Chondroblastic and Fibroblastic subtypes. These histopathologic subtypes, however, do not have influence on the prognosis. Other less commonly encountered histopathologic variations include malignant fibrous histiocytoma-like, small cell, epithelioid, telangiectatic and giant cell-rich (Fig. 59).[1,2,8]
Osteosarcoma. Dense, irregular osteoid separated by a cellular stroma.
Multicenter investigations of different therapies to osteosarcoma of long bones have led to an improved prognosis that now appears superior to that associated with gnathic neoplasms. These protocols involve neo adjuvant (preoperative) chemotherapy followed by radical surgical excision with careful pathologic examination of the specimen to evaluate the chemotherapeutic effects on the tumor. Adjuvant (postoperative) chemotherapy is used and may be modified if poor histopathologic response to the neoadjuvant regimen is noted. Some investigators have demonstrated 4-year survival rates exceeding 80% with this approach Limited numbers of patients with jaw osteosarcomas have been treated with these protocols, and superior results have been claimed compared with surgical treatment alone.[1,2]
Sinonasal EWS/PNET most commonly occur in the maxillary sinus and nasal fossa and mandible [1,2,8] Symptoms include pain, mass, and obstruction. The tumor can be polypoid when arising from the nasal cavity. Bony erosion may or may not be present [2,8]
The tumor is composed of densely distributed, uniform, small to medium sized, round cells with a high nuclear to cytoplasmic ratio and fine chromatin. Mitotic activity is high, and coagulative necrosis is common. Some cases show more densely clumped chromatin or a greater degree of nuclear pleomorphism. Home Wright rosettes are rare Fig. 60.[1,2,8]
Ewing sarcoma. Intermediate-sized cells, scanty cytoplasm and increased mitotic figures.
The immunophenotype includes reactivity for CD99 (MIC2, O13, HBA-71, p30/32, and 12E7), vimentin, and on occasion focally for keratins. Some cases express neural markers, such as synaptophysin, S100 protein, NSE, neurofilament protein, GFAP, and chromogranin. Fli-1 (one portion of the gene fusion product of EWS/FLI1) can be detected by immunohistochemistry.[2,8]
Neurofibroma, Schwannoma,Malignant melanoma are common neuroectodermal lesions.
This benign tumor of peripheral nerve sheath phenotype with mixed cellular components, including Schwann cells, perineurial hybrid cells and intraneural fibroblasts.
Symptoms include epistaxis, rhinorrhoea, swelling, mass, obstruction, and pain [1,8]
Neurofibromas are generally submucosal paucicellular lesions. They are composed of spindled cells with wavy, dark-staining nuclei and scanty cytoplasm, in a background of wavy collagen fibres, myxoid stroma and mast cells. The center of the lesion usually shows residual neuritis (Fig. 61).[1,2,8]
Oral neurofibroma. Spindle cells with dark serpentine nuclei are surrounded by a myxoid matrix.
The tumor is diffusely immunoreactive for S100 protein, but the proportion of positive cells is lower than that in schwannoma. CD34 stains the admixed fibroblasts.[2]
A usually encapsulated, benign tumor composed of differentiated, neoplastic Schwann cells.
Less than 4% of schwannomas involve the nasal cavity and paranasal sinuses and they occur in middle aged adults with an equal gender distribution. Sinonasal schwannomas arise from the branches of the trigeminal (5th cranial) nerve and autonomic nervous system, and most commonly involve the ethmoid and maxillary sinuses, followed by the nasal cavity, sphenoid and frontal sinuses. The presenting symptoms include obstruction, rhinorrhea, epistaxis, anosmia, headache, dysphagia, hearing loss facial or orbital swelling, and pain Sinonasal schwannoma ranges in size up to 7 cm. It is a well-delineated but non-encapsulated globular, firm to rubbery yellow-tan mass. The cut surfaces show tan-grey, yellowish, solid to myxoid and cystic tissue, commonly with hemorrhage.[1,2,8]
Schwannoma is composed of cellular Antoni A areas with Verocay bodies and hypocellular myxoid Antoni B areas. The cells are fusiform with elongated fribillary cytoplasm, and buckled to spindled nuclei which show little pleomorphism, although scattered large pleomorphic or bizarre cells can be present in some cases. Nuclear palisading is often evident in some foci. There are frequently small to medium-sized vessels with ectasia, thrombosis and perivascular hyalinization in the Antoni B areas. Extensive degenerative changes can occur, and may result in only a thin rim of recognizable tumor. Cellular variants exhibit only the Antoni A pattern, but no fascicular growth or Verocay bodies (Fig. 62).[2,42]
Schwannoma cellular areas (Antoni A) and loose, myxoid foci (Anroni B)
More than half of mucosal melanomas occur in the head and neck area (including the oral and sinonasal regions). Symptoms include nasal obstruction, epistaxis, nasal polyp, pain, nasal discharge of variable duration, and melanorrhoea (“coal flecked” or brown nasal discharge (Fig. 63).[1,2,43]
Malignant melanoma involving maxillary sinus and alveolar ridge.
The tumors are comprised of epithelioid, spindled, plasmacytoid, rhabdoid and/or multinucleated tumor cells. The cells are generally medium to large-sized They have a high nuclear to cytoplasmic ratio with pleomorphic nuclei containing prominent eosinophilic nucleoli and intranuclear cytoplasmic inclusions. Nuclear molding may be present. The cytoplasm is usually densely eosinophilic, and variably contains melanin pigment. Mitoses, including atypical forms, are frequent and easily identifiable. Vascular invasion and neurotropism may be identified in up to 40% of cases. An inflammatory infiltrate admixed with pigment-laden histiocytes is commonly identified within or adjacent to the tumor. Tumor cell necrosis is common, particularly in tumors displaying a peritheliomatous or pseudopapillary growth pattern. Other growth patterns include solid, alveolar or sarcomatoid (Fig. 64). [1-8]
Malignant melanoma expresses S100 protein, vimentin and variably HMB45, tyrosinase, melan-A and microphthalmia transcription factor. Neuron specific enolase, CD117, CD99 synaptophysin, CD56, and CD57 have been reported to be occasionally positive but epithelial membrane antigen, cytokeratins, and muscle markers are not expressed. [2,43]
Malignant melanoma. Malignant cells with a high nuclear to cytoplasmic ratio with pleomorphic nuclei containing prominent eosinophilic nucleoli.
The features best related to tumor behavior are the stage of disease and the depth of invasion. Surgical excision is the mainstay of treatment although the extent of the excision is somewhat controversial. Older literature suggests that surgical margins of 3 to 5 cm around the tumor are necessary to achieve control, regardless of the site of the lesion. More recent studies indicate that a 1-cm margin is adequate for small cutaneous tumors less than 2 mm in thickness. For larger, more deeply invasive tumors, wide surgical excision still is recommended.[1,2,8]
Although heavily exploited in recent decades, the domain of oxide nanostructures remains of interest to researchers throughout the world. This is because that the shapes and sizes of oxide nanomaterials greatly influence their properties, which is reflected in their use in the most diverse fields [1, 2]. Oxide nanostructures have applications in catalysis, energy storage, environmental decontamination, microelectronics, medical technology, ceramics, cosmetics, and so on [3, 4, 5].
Among the most studied branches of nanostructures are metal oxides, with representatives such as TiO2, ZnO, CuO, Fe3O4, WO3, Cr2O3, Co3O4 [6].
The structure, morphology, and properties of the oxide nanostructures depend significantly on the obtaining method. A large number of available synthesis methods underlies the continuous interest in obtaining oxide nanostructures that can be used successfully in specific areas [1, 7]. However, most of these methods are limited due to the use of toxic reagents, high processing temperatures, high vacuum, expensive equipment, or long reaction times [8, 9].
Although physical methods have the advantage of high reproducibility, chemical methods in the liquid phase are more often used to obtain oxide nanostructures due to their advantages, such as low production temperature, homogeneous mixing of precursors at the molecular scale, design and control of the physico-chemical properties of final products, depending on the precursors, and the experimental conditions used [10, 11].
Among the various chemical procedures, the sol–gel method gained increasing importance in the field of materials science because it is cheap, simple, allows the introduction of dopants in large quantities, ensures high purity, and homogeneity, allows control of size, shape, and size distribution of the obtained nanomaterials [12, 13, 14].
Lately, for the preparation of functional nanomaterials, more and more attention is being paid to the use of microwave as the energy source for carrying out a chemical reaction [1, 15]. The microwave (MW) assisted sol–gel method is reported to be a simple, cheap, faster, more energy-saving, and efficient process as compared to conventional heating methods [16, 17, 18]. The use of microwaves has received increased attention in the technological field because, among other things, it reduces the reaction time from days to minutes or hours, improves the properties of synthesized nanostructures, and allows obtaining oxide nanocrystalline films on various substrates [8, 19, 20].
The improved properties of the oxide nanostructures obtained by microwaves assisted sol–gel method could be correlated to the influence of the microwaves on the chemical reactions that take place during the sol–gel synthesis, leading to the formation of different molecular species. Results on the influence of the microwaves on the chemical reactions during the sol–gel synthesis will be discussed in the present chapter.
Among the chemical methods in the liquid phase, the sol–gel technique is a versatile and efficient method for pure or doped metal oxide films or powders, as well as for oxide compounds preparation [21, 22, 23, 24].
A comprehensive definition of sol–gel method assumes that the process represents the formation of an inorganic polymeric network by reactions in the solution at low temperatures. In the second step, by adequate thermal treatments, the conversion of the inorganic amorphous polymers takes place either into glasses or into crystalline materials [1, 22].
Based on the type of the precursors and the reaction medium used, two types of sol–gel processes were developed: on the bases of the alcoholic (organic) or aqueous medium.
According to Pierre [25] in both polymeric and aqueous sol–gel routes, the precursors undertake the succession of the following transformations in the presence of water:
In the case of the polymeric route, using alkoxides (non-ionized precursors), the reactions that occur are the following:
The aqueous sol–gel route has also two pathways: the colloidal route [26] and the aqueous route using different chelating agents [23, 26, 27].
In the case of the aqueous route, which starts from colloidal solutions in aqueous medium, the following reactions take place:
In the case of transition metals, it is more difficult to obtain gels, the metals having very high reactivity due to their higher electronegativity and their not satisfied coordination sphere.
To favor the gelling process, in case of the transition metals, chelating agents, as carboxylic acids or polyols, are used. A typical reaction is the following
It is important to underline that in all mentioned cases the reactions take place simultaneously, not consequently, and they are also reversible, fact that determines a complex composition of the sol–gel solutions.
Prior to gelation, the sol–gel solution can be used to obtain thin films by using simple techniques such as dip or spin coating [23, 28].
Besides the fact that it offers the possibility of obtaining both films and powders of metal oxides at nanometric dimensions, the sol–gel method has also some advantages over other preparation techniques. Such advantages are purity, homogeneity, the possibility to introducing dopants in large quantities, ease of manufacturing, low processing temperature, control over the stoichiometry, composition, viscosity [13, 27, 29] and, in the case of thin films, easy control of thickness, as well as the ability to cover large and different type of surfaces [30, 31].
Lately, ultrasonic [32, 33] or microwave irradiation [9, 17, 18, 34, 35, 36] in sol–gel oxide nanomaterials synthesis have become methods of interest because, in addition to being cheap and environmentally friendly heating methods, offer the advantage of using shorter synthesis time, and allow the control of crystallinity, size and morphology of the resulted nanoparticles [9, 35].
Microwave radiation is a source of energy of great interest for chemical synthesis because, among other benefits, it has been observed that the use of microwaves improves the properties of obtained nanomaterials. The first reporting on the use of microwaves in a chemical synthesis dates back to 1986 [37]. Although initially microwaves have been applied in organic synthesis, lately their use has become quite widespread in obtaining inorganic products like metal oxides nanomaterials and metallic nanomaterials [38].
Microwaves are electromagnetic radiations located between infrared radiation and radio waves with frequencies between 300 MHz (100 cm) and 300 GHz (0.1 cm). For the nanomaterials synthesis in which aqueous solutions are used, 2.45 GHz frequency is commonly applied for microwave heating of the solutions, because water absorption is maximum at this value.
Subjected to a microwave field, the substances behave differently: absorb, transmit, reflect received radiation, or any combination of these three interactions. Polar substances absorb microwaves radiation, non-polar substances are transparent environments for this type of radiation, and electrical conductors reflect microwaves radiation. Therefore, microwave heating process is used for heating the materials which can absorb the microwave energy and convert it into heat especially by dipolar polarization or conduction mechanism [1, 40]. The interactions of polar molecules and ions with the electromagnetic field have already been described by many researchers. Shortly, the collisions resulting from the rotation of the dipoles during polarization and the load carriers during conduction give energy to the atoms and molecules from the solution in the form of heat [38, 40].
While conventional heating methods are slow enough and the heat transfer from the surface to the inner material or solution, producing non-homogeneous heating, microwave heating is done quickly because microwaves can penetrate the materials to a depth that depends on the dielectric properties of the material, heating them homogeneously [38]. Consequently, microwave heating can have certain benefits over conventional heating, like faster reaction, higher reproducibility, enhancement of product quality. It is instantaneous, with no heat dissipation effects, and advantageous for selective dielectric heating, as a result of the dielectric constant difference between the solvent and reactant [39].
In sol–gel synthesis, due to rapid and direct heating of the sample with microwave radiation, the instantaneous decomposition of the precursors and the obtaining of a supersaturated solution occur. In this way, the conditions for obtaining monodispersed nanoparticles (rapid and short nucleation in a supersaturated solution) can be obtained experimentally. At the same time, the in-situ approach of conversion of energy results in a minimized thermal gradient due to the fast heating rate consequently is providing perfect conditions for the uniform growth of nanocrystals [31, 41].
More, in the case of sol–gel synthesis using organic solvents, characterized by slow kinetics, microwave heating is an optimal method of increasing the rate of reaction [41].
From the research carried out so far, it has been observed that, by combining the sol–gel method with the microwave heating, the properties of the obtained oxide nanostructures are improved [9, 34].
Because the presence of MW, the interaction of the electromagnetic field with each molecule in the solution differs during the hydrolysis-condensation process, we can expect the formation of different molecular species as compared to the classical sol–gel synthesis.
Up to now, there have been several reports regarding the synthesis of metal oxide nanomaterials by microwave-assisted sol–gel method. However, many of them have been performed using domestic microwave ovens, in which the reaction conditions cannot be accurately measured, making the experiments difficult to be reproduced.
According to the literature data, the MW irradiation in the sol–gel synthesis was used, most frequently, for precipitation of nanocrystalline metal oxides, for thermal treatment of amorphous oxide nanopowders as well as for drying and thermally treatment of the oxide films [36].
Less attention was given to study the reactions that take place in the sol–gel solutions during MW irradiation [42, 43, 44, 45].
A large number of oxides were prepared by sol–gel and microwave assisted sol–gel methods. Using MW irradiations of the solutions, preparation of several oxides were mentioned in the literature data, as MgO [46], RuO2 [47], ZnO [16], ZrO2 [48], WO3 [49], SiO2 [50], TiO2 [35, 51]. The power of the used microwaves ranged from 140 W [51] to 850 W [47].
Among them, considerable interest is given to pure and doped TiO2. The doping of TiO2 was realized with a high number of elements, such as Cr [13], Ag [52], Au, Pt [14, 53], Sn-Cu-Ni [54], Fe, Pt, Pd [51] and V [55]. Doping TiO2 with different elements the properties of the resulted nanostructures are improved, while using microwave assisted preparation, supplementary improvement was also observed.
Our studies regarding the influence of the microwaves on the reactions in the sol–gel solutions were published by Predoana et al. [42] in the case of TiO2 and V-doped TiO2 nanostructures.
The use of vanadium as a doping agent has a beneficial influence on the TiO2 properties: it can reduce the band gap energy, enhance the absorption of visible light and increase the specific surface area of the powder. The mentioned properties are reflected mainly in its photocatalytic activity, previously presented by Huang et al. [55].
In our studies, the reagents used in the synthesis were titanium(IV) ethoxide Ti(OC2H5)4 in the case of TiO2, as well as, titanium(IV) ethoxide Ti(OC2H5)4 and vanadylacetylacetonate VO(AcAc), for V-doped TiO2. In both cases, ethanol C2H5OH as a solvent, 2,4 pentanedione (AcAc), as a chelating agent, and nitric acid HNO3 as catalyst were used.
By the classical sol–gel method the reagents were mixed for 2 hours at room temperature. By the microwave-assisted sol–gel method, the same mixture was exposed for 5 min at 300 W and a frequency of 2.45 GHz.
The first important result of using the microwave-assisted sol–gel method is the significantly increasing of the stability of the prepared solutions against gelation, having a great advantage for multilayer film deposition. This effect was assigned to the formation of different molecular species.
The solutions were used for obtaining thin films and the resulted gels were investigated for their structural and morphological properties.
In our studies for TiO2samples synthesized by sol–gel and microwave-assisted sol–gel methods, the TG/DTG/DTA curves corresponding to the decomposition of the obtained gels are presented in Figure 1.
TG/DTG/DTA curves of the TiO2 samples obtained by SG and MW methods [42] (Reproduced with the permission of Springer Nature).
It could be noticed that the thermal decomposition of the gels is not essentially influenced by the method of preparation. Only a small increase of the thermal effect at 195o C is observed for the TiO2 sample obtained by MW assisted sol–gel method. The fact could be explained by the positive influence of microwaves on the formation of the molecular species that decompose at the mentioned temperature.
Based on the TG/DTG/DTA results, the samples prepared by both methods were thermally treated at 450°C for 1 h. By X-ray diffraction of the samples thermally treated at this temperature only anatase phase was detected (according to JCPDS card no. 21–1272), but a higher crystallinity is noticed in the case of sample obtained by MW-assisted procedure (Figure 2).
The XRD patterns of the TiO2 samples obtained by SG and MW-assisted SG methods thermally treated at 450°C.
In the case of the V-doped TiO2 the TG/DTG/DTA measurements in the air are presented in Figure 3 for the gel containing 2 mol% V. In this case, increased thermal stability and a more complex decomposition of the gels obtained by the microwave-assisted sol–gel method is observed.
TGA/DTG/DTA curves of the V-doped TiO2 samples obtained by SG and MW-assisted SG methods [42] (Reproduced with the permission of Springer Nature).
Confirmations of the TG/DTG/DTA results on the gels with 2 mol% V were obtained by Differential Scanning Calorimetry (DSC). The obtained DSC curves are presented in Figure 4.
DCS curves of the V-doped TiO2 obtained by SG and MW-assisted SG methods [43] (Reproduced with the permission from Springer Nature).
According to the DSC results, the thermal stability of the gel obtained from the solution prepared in the presence of microwaves, is significantly higher (with about 100°C), as compared with the gel with similar compositions, but obtained by the classical sol–gel method.
At the same time, the number and temperatures of the thermal effects are different in the two discussed cases underlying the different compositions of the gels obtained in the presence or the absence of the microwaves.
The TG/DTG/DTA/EGA measurements, presented in Figure 5, have confirmed, once more, the results discussed above, regarding the different thermal behavior of the gels obtained by the microwave-assisted sol–gel method.
TG/DTG/DTA/EGA curves of V-doped TiO2 obtained by (a) SG and (b) MW-assisted SG methods [42] (Reproduced with the permission of Springer Nature).
In the case of the microwave-assisted sol–gel method the same gasses are evolved, namely H2O and CO2, but a more complex thermal decomposition is observed, with different ratios among the two mentioned gases at the different temperatures. This result is assigned to the higher number of molecular species present in the gel, having different chemical composition and different thermal stability.
By X-ray diffraction of the V-doped TiO2 with 2 mol% V samples thermally treated at 450°C (Figure 6) only anatase phase was detected (according to JCPDS card no. 21–1272). As in the case of un-doped TiO2, a higher crystallinity is noticed in the case of samples obtained by MW assisted procedure.
The XRD patterns of the V-doped TiO2 samples obtained by SG and MW-assisted SG methods, thermally treated at 450°C.
Before gelation, the solutions prepared in the presence and in the absence of MWs were used for thin film deposition by dip-coating on glass substrates [43].
In our studies for the TiO2films obtained by the sol–gel method, the SEM micrographs show surface cavities that were not observed in the case of microwaves-assisted sol–gel films (Figure 7a and c).
SEM micrographs showing the film cross-section for samples (a) (TiO2)SG; (b) (TiO2)MW; (c) (V-dopedTiO2)SG; (d) (V-dopedTiO2)MW [43].
The sol–gel TiO2based films present also a similar variation of the morphology according to the method of preparation. A more dense and homogeneous aspect is observed in the film obtained in the presence of microwaves (Figure 7b and d).
Thickness values are around 200 nm both for TiO2 and V-doped TiO2 films, but slightly higher in the case of the films obtained from microwave-assisted sol–gel solutions.
The transmission spectra of obtained films are presented in Figure 8 show optical transmittance values mainly over 80% in the visible range.
Optical transmission of the TiO2 and V-doped TiO2 films obtained by (a) SG and (b) MW-assisted SG methods.
To explain the differences induced by the microwave-assisted sol–gel process on the properties of the resulted films, their influence on the starting solution, and the evolution of the sol–gel process, should be taken into consideration. Based on the results obtained up to now, it could be assumed that in the presence of microwaves, different and more stable molecular species are formed as compared to the classical sol–gel method and this a fact influences the properties of the resulted films.
It was also observed that the effect of microwaves on the properties of the resulted materials is higher in the case of V-doped TiO2 samples, fact that could be correlated to an enhancement of the reactions between Ti and V reagents during the sol–gel process in the presence of the microwaves.
As presented in the several references, WO3based nanomaterials are widely investigated in the field of electrochromic devices [56], gas sensing [57], and photocatalysis [58] in different morphologies and structures. Even though the sol–gel process has a long past and is an intensely researched method [59] the literature of sol–gel preparation of WO3 using microwave-assistance is scarce. The following articles are all from the 2010s so further researches are to be expected.
Different nanostructures were prepared by microwave assisted sol–gel method with sodium tungstate as a precursor material by Kharade et al. [60, 61, 62]. The research group synthesizes various nanoparticles and nanofilms for electrochromic purposes. In 2012 WO3 nanofilms were deposited on the FTO substrate, which was the first time used MW-assisted two-step process. In the first step, the preparation of the gel was conducted with microwave assistance, then in the second step, the deposition of the thin film occurred by a chemical growth set up. Scanning electron microscope (SEM) showed that the surface is coated with petal-like WO3 nanodisks with dimensions of 450–600 nm length, 350–400 nm width, and 20–35 nm thickness. The X-ray diffraction (XRD) analysis (Figure 9) points out that WO3 is in the hexagonal crystal form. Narrow and intense XRD peaks indicate that the material has good crystallinity and calculations determined that the crystal size is 71 nm, which is comparable to samples made by the regular sol–gel method [63]. X-ray photoelectron spectroscopy (XPS) revealed that the W:O ratio is non-stoichiometric(2.89). Electrochromic capabilities were determined with different electroanalytical methods [60]. Comparing this to a regular sol–gel method shows that the morphology of the surface, namely the platelet like nanodisks is nearly the same with a small difference in size (regular sol–gel platelets: 10–30 nm thick and few hundred nm lengths and width). However, to achieve the same crystallinity a 500°C annealing process is required for the regular sol–gel method, in contrast to the 150°C drying of the MW-assisted sol–gel method [64].
X-ray diffractogram of the WO3 thin film [60] (Copyright (2012), with permission from Elsevier).
The same hexagonal WO3 thin film was synthesized and its electrochromic properties were enhanced with different amounts of Ag nanoparticles [61]. The microwave-assisted sol–gel method was also used to produce WO3/MoO3 mixed oxide thin films. First, the WO3 layer were produced with the two-step method explained earlier, then MoO3 was deposited with vacuum evaporation [62].
Hilaire et al. [49] prepared WO3 nanoparticles using a nonaqueous microwave-assisted sol–gel method for photoanodes. The synthesized nanoparticles were analyzed with FT-IR, which showed that no organic contaminant remained on the surface of the particles, but a weight indicates that there are a 4.4% water and organic residue after 800°C heating. XRD studies confirm the monoclinic crystalline structure of the WO3 nanoparticles.
Transmission electron microscopy (TEM) showed that the platelets like WO3 nanoparticles size is 20–40 nm and thickness of 3 nm. Moreover, TEM measurements indicate that the WO3 platelets face having the crystalline orientation of [0 0 2]. The WO3 nanoparticles were used for the production of photoanodes, which was proven to be an efficient method for water splitting. The comparison of this result with another nonaqueous regular sol–gel method shows that the morphology of the particles differs, but this can be caused by the usage of a different solvent (dicarboxylic acid) and modifier (polyethylene glycol).
The regular method resulted in larger (58 nm) rod-like nanoparticles. The case of the WO3 particle’s crystallinity is similar to the thin layer’s: without after annealing process, the MW assisted method provides better crystallinity [65].
It was also established [66] that microwave heating is more convenient than resistive heating to fabricate WO3 nanoparticles with high specific surfaces and very small particle sizes also in the case of hydrothermal method of preparation. In our studies [67, 68] hexagonal structured WO3 nanoparticles and wires were prepared using MW assisted hydrothermal process. SEM images are presented in the Figure 10.
SEM images of the (a,b) hexagonal WO3 nanowire coated with TiO2 and (c, d) monoclinic WO3 nanoparticle coated with TiO2 [67] (Reprinted with permission from [67] copyright from RSC Advances).
The Au decorated h-WO3 nanowires were prepared for photocatalysis. The pre-decorated WO3 nanowires showed crystallinity and were composed of W and O only. The morphology also differs from nanodisks, the hydrothermally produced WO3 took the form of nanorods with 10 μm length and 10 nm diameter.
Nevertheless, the Au decorated nanowires showed great photocatalytic activities. Nanowires and nanoparticles coated with TiO2 using ALD were also synthesized, but the characteristics of the non-coated samples were done. Hexagonal and monoclinic nanoparticles were prepared using controlled annealing of the samples.
Similarly, further annealing is needed to reach a comparable crystallinity, but for the monoclinic structure it’s obligatory. The size of the crystals was 50–70 nm and 60–90 nm for hexagonal, and for the irregular shaped monoclinic WO3 nanoparticles respectively. The hexagonal WO3 nanowires were analogous to the earlier nanowire, several μm long and 5–10 nm diameter. The TiO2 coated nanostructures proved to be efficient photocatalysts [67, 68].
Let us deal with the results regarding the synthesis by microwave-assisted sol–gel methods of the precursor powders for SrCu2O2 preparation.
The interest for the SrCu2O2 compound are connected to its possible applications as thermoelectric or full oxide electronic devices, solar cells, liquid-crystal displays, touchscreen, and so on [45].
Among the CuO-based p-type TCOs, Cu-Sr-O has received attention due to its wide direct band gap, and its potential use in transparent optoelectronic devices; such as light-emitting diodes, laser diodes, solar cells, display technology, and other technologies [69]. In most of the published reports, Cu based p-type TCO thin films are deposited by high vacuum processes which are costly. Some of the processes include pulsed laser deposition (PLD), reactive evaporation, magnetron sputtering, thermal co-evaporation and radio frequency [70, 71, 72, 73, 74, 75, 76]. To date, few studies have reported on the preparation of a Cu-based p-type TCO by a non-vacuum solution chemical route.
Roy et al. [77] used sol–gel and annealing methods to prepare Cu2SrO2 thin films. They used different oxygen pressure, annealing time, and temperature combinations to attempt to obtain phase pure Cu2SrO2 thin films. Copper (II) methoxide and triethanolamine were mixed in the ration 1:1. Pure Sr-metal was dissolved separately in distilled anhydrous isopropanol under argon. The Cu-solution was then mixed drop-wise into the Sr-solution while stirring. The mixture was stirred continuously for 2 hrs at room temperature. The sol was spin-coated on clean substrates with 3000 rpm for 30 s. The coated films were heated at 225°C for 2 min in the air for partial pyrolysis. This coating/heating cycle was repeated ten times to obtain films of the desired thickness of 500 nm. After deposition, the film was annealed further under controlled oxygen pressure. Different annealing procedures were used to avoid the presence of excess Cu2O phase.
XRD analysis (Figure 11b) showed the films had a mixed-phase of excess Cu2O and Cu2SrO2 after final reduced-oxygen pressure annealing. Films annealed at lower oxygen pressure (1.3 × 10−2 and 1.3× 10−3 Pa) had similar phase composition and in all the three films Cu2O formed as a secondary phase with Cu2SrO2. For the film annealed at the highest oxygen pressure (1.3 × 10−1 Pa), CuSrO2 was observed as the amount of Cu2SrO2 decreased and the intensity of the Cu2O peaks did not change.
(a) TEM image, (b) XRD spectra (c) SEM image of the films after final annealing at 750°C under 1.3 × 10−2 Pa oxygen pressure [77] (Reproduced by the permission of Elsevier).
Both SEM and TEM images (Figure 11a and c) show that two phases are present. The light-gray particles (differing sizes) in the SEM and large particles in TEM images are the Cu2SrO2 phases. The dark gray phase in the SEM image is a mixture of small Cu2SrO2 and Cu2O particles, as confirmed by the TEM images. The SEM and TEM images reveal that the Cu2O and Cu2SrO2 phases are intermingled with each other.
Ginley et al. [78] used sol–gel and annealing to prepare pure phased Cu2SrO2 films. Stoichiometric amounts of aqueous solutions copper formate and strontium acetate were mixed in methanol and stirred. Triethanolamine was added, the mixture stirred and evaporated at 80°C to form sol which was diluted by isopropyl alcohol and spin-coated on MgO (100) substrates for 20 s, at 3000 revs per min. The resulting films were annealed at 200°C temperature for 2 min and then pyrolyzed at 500°C for 2 min. The spin-coating and pyrolysis cycles were repeated 8–10 times. After the cycles, the films were first annealed at 750°C for 30 min in air and then at 775°C under 2.7 × 10−6 Torr oxygen. The films were characterized by XRD (Figure 12) and FTIR and showed to be phase pure.
XRD patterns of Cu2SrO2 films as a function of processing time [78].
Predoana et al., are the first to report the synthesis of Sr-Cu-O gels by microwave (MW) assisted sol–gel methods [45]. Pure strontium acetyl acetonate (Sr(C5H7O2)2 and copper (II) acetyl acetonate (Cu(C5H7O2)2) were used as precursors for strontium and copper, respectively. The 0.25 M aqueous solutions of Sr.(C5H7O2)2 and Cu(C5H7O2)2 solution in absolute ethanol were mixed with triethanolamine, in the ratio 1:1. In the case of the sol–gel method, the starting solution was homogenized under vigorous stirring for 2 h at 80 C. For MW assisted sol–gel method, the same starting solution was homogenized by stirring and exposing to microwaves having power ~ 300 W and 2.45 GHz frequency for 5 minutes. The sol–gel and the microwave-assisted sol–gel prepared Sr-Cu-O were characterized by SEM, FTIR, XRD, and their thermal properties investigated by TG/DTA-MS in air, inert and reducing atmospheres.
In the experimental conditions presented above pieces of gels of different size, and blueish-green color were obtained for both preparation methods. The results obtained by TG/DTA-MS analysis (Figure13a and b) of the obtained gels demonstrated the influence of MW on the sol–gel synthesis. MW treated samples had one more mass loss step when heated in air attributed to complex compositions of the resulted gels that contain a higher number of molecular species with higher thermal stability. The results were confirmed with the FTIR spectra (Figure 13c and d) showing more vibration bands for the samples prepared by the MW sol-gel method, assigned according to [79, 80, 81].
Thermal decomposition in air (a) sol–gel synthesized sample, (b) MW assisted sol–gel synthesized sample, (c) FTIR spectra of sol–gel synthesized sample, (d) FTIR spectra of MW assisted sol–gel synthesized sample [45] (Reproduced by the permission of Elsevier).
Based on the XRD patterns of the residues (Figure 14), the final product is composed of a mixture of phases that depend on the synthesis route and the annealing conditions.
(a) XRD patterns of sol–gel synthesized samples (b) MW-assisted sol–gel samples annealed at 900°C in air, N2 and 5%H2/95%Ar [45].
For samples annealed in air, Sr–Cu–O phase was also present for the sol–gel synthesized sample, while the MW sample had CuO as the main component. In different atmosphere (N2 and H2/Ar) several compounds (Sr2CuO3, SrO and CuO) are present in varying amounts. Only traces of SrCO3 can be detected. In all annealing atmospheres, in the case of the samples synthesized by MW-assisted sol–gel method, powders with a lower degree of crystallization is formed. This result could be attributed to the formation of a higher number of molecular species with higher thermal stability.
The powders prepared in the mentioned conditions are intended to be investigated as precursors for SrCu2O2 compound preparation.
The presented results are important revealing the effect of MW on the reactions that take place during the sol–gel synthesis but should be considered preliminary. Direct methods of the solutions investigations, as High-Pressure Liquid Cromatogaphy (HPLC), are underway in order to bring more information on the sol–gel chemistry in the presence and the absence of microwaves.
The interest of using microwaves in obtaining oxide nanostructures by reactions in solutions is rather high, leading to obtaining powders or films with enhanced properties.
According to the literature data, the MW irradiation in the sol–gel synthesis was used, most frequently, for precipitation of nanocrystalline metal oxides, for thermal treatment to crystallize the amorphous oxide nanopowders as well as for drying and thermally treatment of the oxide films.
However, the influence of the microwaves on the chemical reactions that take place during the sol–gel synthesis is less investigated.
Results regarding the formation of pure or doped nanostructures, as well as oxide compound, by sol–gel method in the presence or absence of microwave are presented.
The main results of the studies have shown that in all cases in the presence of microwave formation different molecular species is observed with a positive influence on the properties of the resulted nanostructure.
The advantage of using the MW-assited sol–gel method is a more shorter time of synthesis and obtaining nanostructures with improved properties.
The obtained results are of interest, but could be considered preliminary and systematic studies on the chemical processes induced by the microwaves should be continued.
This work was performed in the frame of Mobility Project “Reduced semiconductor oxides for TCO, photocatalysis and gas sensing applications”, 2019– 2021, between IlieMurgulescu Institute of Physical Chemistry of the Romanian Academy, Bucharest, Romania and Research Center for Natural Sciences, Hungarian Academy of Science Research Group of the Hungarian Academy of Science at the Budapest, Hungary. An NRDI K 124212 and an NRDI TNN_16 123631 grants are acknowledged. The research within project No. VEKOP-2.3.2-16-2017-00013 was supported by the European Union and the State of Hungary, co-financed by the European Regional Development Fund. The research reported in this paper was supported by the BMENanotechnology and Materials Science TKP2020 IE grant of NKFIH Hungary (BME IE-NAT TKP2020)and Stipendium Hungaricum scholarship grant.
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\n\nIntechOpen’s co-founders, both scientists themselves, created the company while undertaking research in robotics at Vienna University. Their goal was to spread research freely “for scientists, by scientists’ to the rest of the world via the Open Access publishing model. The company soon became a signatory of the Budapest Initiative, which currently has more than 1000 supporting organizations worldwide, ranging from universities to funders.
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