Genetic Revelation of the Potentially Malignant Disorders in the Oral and Maxillofacial Region

Abstract

The oral and maxillofacial region is the site of numerous cancer forms. The most frequent cancer, which accounts for more than 90% of these tumors, is squamous cell carcinoma. Genetic changes caused by malignant transformation later result in phenotypic changes in cells. Potentially malignant disorders and circumstances can lead to the development of some malignancies, such as oral squamous cell carcinomas (OSCCs). Because OSCC and precursor lesions cannot be detected early, the 5-year survival rate for OSCC is still only about 50%. Early detection of oral cancer, particularly in the premalignant stage, can greatly reduce death and morbidity. The clinical, histological revelations and etiopathogenesis of a few potentially malignant disorders of the oral and maxillofacial region are reviewed in this chapter.

1. Introduction

Cancer is a collection of disorders have been designated by unusual proliferation of cells and the capacity to migrate or spread to other regions of the body [1]. According to Global Cancer Statistics 2022, more than 19.3 million (19,300,000) new cancer cases were diagnosed and recorded recently, resulting in nearly 10 million fatalities by 2020 [2]. According to projections made by the American Cancer Society, it was estimated that in the year 2022, there would be a total of 1,918,030 newly diagnosed cases of cancer and 609,360 deaths attributed to cancer in the United States [3]. Oral and maxillofacial cancer is one of the most common kinds of cancer, and it is becoming a growing concern in numerous regions of the world [4]. Oral cancer is the sixteenth most prevalent malignancy and the fifteenth leading cause of death globally, with an incidence of four cases per 100,000 people (age-adjusted), with substantial regional differences depending on gender, age groups, nations, races and ethnicities, and socioeconomic conditions [5]. Geographical location is a significant role in the development of oral cancer since persons with poor socioeconomic class are more likely to get the disease because they are less aware of the dangers of avoidable risk factors such as tobacco, areca nut, and alcohol use [6]. In South Asian nations such as India, Sri Lanka, Pakistan, and Bangladesh, it is the most prevalent kind of oral cancer and accounts for around one-fourth of all new cases [4].

Oral cancer may originate through two primary pathways: de novo development or progression from potentially malignant disorders. These lesions commonly manifest as leukoplakia (characterized by a white patch), erythroplakia (characterized by a red patch), or erythroleukoplakia (characterized by a mixed red and white patch) [7]. Squamous cell carcinoma (OSCC) is the most prevalent cancer, accounting for more than 90% of all malignancies, and it develops from potentially malignant lesions and conditions in the oral and maxillofacial facial region [8]. There are several stages to the development of oral cancer from potentially malignant disorders, including genetic, epigenetic, and metabolic changes [5, 9, 10, 11]. Genetic alterations that arise during the process of carcinogenesis can manifest as various types of genomic changes, including point mutations, amplifications, rearrangements, and deletions [12]. Proto-oncogenes undergo a conversion process that leads to the formation of oncogenes. These oncogenes are responsible for modifying the protein sequences of growth-promoting proteins and factors that regulate the cell cycle. Consequently, uncontrolled cell division occurs weakening cell cohesion and causing local infiltration, which plays a crucial role in the progression from dysplasia to oral squamous cell carcinoma (OSCC) [13]. Numerous oncogenes play a vital role in cellular responses, and these include the proto-oncogene epidermal growth factor receptor (EGFR/c-erb 1), various members of the ras gene family, c-myc, int-2, hst-1, PRAD-1, bcl-1, and the growth regulator P53 [14].

The management of oral squamous cell carcinoma (OSCC) has undergone significant transformations; in recent years, primarily due to the emergence of immunotherapy, in addition to conventional approaches such as surgery, systemic therapy, and radiotherapy, either as individual therapies or in combination. Nevertheless, a significant proportion of cases are typically identified during the later stages of the ailment, resulting in a substantial reduction in the overall survival rate among affected individuals [15]. The most effective approach to preventing the transformation of cancer is through the early detection of potentially malignant disorders, which involves regular oral examinations and the removal of environmental and behavioral risk factors that are associated with such lesions [16, 17].

In this chapter, the epidemiology and clinico-histological aspects of numerous forms of potentially malignant disorders in the oral and maxillofacial region will be briefly discussed. Their risk factors, genetic and epigenetic underpinnings, early detection approaches, and therapy to prevent the development of malignancies will also be emphasized.

2. Methodology

The chapter was prepared by conducting a thorough review of the existing literature on potentially malignant disorders in the oral and maxillofacial region from the reputable scientific databases, including PubMed, Scopus, ScienceDirect, Google Scholar, and Cochrane using Boolean operators. The article search was carried out using relevant keywords. The inclusion criteria for preparing this chapter were articles about genetic aspects of OPMDs published online, articles in English, and articles with both experimental and observational research. Incomplete and inaccessible articles were excluded. Data retrieval began with selecting and determining literature that was relevant to the objectives and met the inclusion criteria. Next, literature that met the inclusion criteria was extracted. Data extracted from each piece of literature included author, year of publication, title, and journal name. Studies that specifically examined the genetic aspects of these disorders were carefully selected. Through a critical analysis of the chosen studies, the information was synthesized to provide a cohesive and informative overview of the genetic revelation of potentially malignant disorders in the oral and maxillofacial region. The methodology implemented here ensured the inclusion of proper references and allowed peers to reproduce the experiments and obtain consistent outcomes.

3. What are the potentially malignant disorders of the oral and maxillofacial region?

Usually, the clinical appearance regarding oral cancer is tremendously varied along with symptoms as well as signs, which are very often related to the primary tumor. Several cause are responsible to generate oral cancer for instance oral cavity lesion, ulcerated lesion, mobile teeth, bleeding, pain or numbness in the mouth or face, ill-fitting dental prosthesis could cause oral cancer. Leaving apart, viral lesions (warts), and even white lesions can be considered as malignant on biopsy. Erythematous (abnormal redness of mucous membrane) lesion, which is found during biopsy of erythroplakia, can also induce suspicion of oral cancer. However, various potentially malignant disorders of the oral and maxillofacial region are listed in the Table 1 below [18]:

Potentially malignant disorders of the oral region	Potentially malignant disorders of the maxillofacial region
Leukoplakia	Actinic cheilitis
Proliferative verrucous leukoplakia	Actinic keratosis
Erythroplakia	Epidermolysis bullosa
Oral submucous fibrosis	Dysplastic nevi
Oral lichen planus and oral lichenoid reaction	Congenital melanocytic nevus
Lichenoid dysplasia	Sebaceous Nevus

Table 1.

Potentially malignant disorders of the oral and maxillofacial region.

Some of the potentially malignant disorders of the oral and maxillofacial region, which has the potency for the malignant transformation will be discussed in this chapter.

4. Epidemiology of potentially malignant disorders of the oral and maxillofacial region

Understanding the epidemiology of potentially malignant disorders of the oral and maxillofacial region is crucial for effective prevention and management strategies. This summary explores the current updates on the epidemiology of potentially malignant disorders, including age, sex, changes in prevalence, geographical and demographic patterns, and the impact of public health interventions.

Age and Sex: Potentially malignant disorders can affect individuals of all age groups, with older adults being more susceptible due to cumulative exposure to risk factors, such as tobacco and alcohol use. Regular oral health screenings become increasingly important as individuals age to detect and manage lesions early. In terms of sex, studies suggest that males have a higher incidence of potentially malignant disorders, possibly due to higher rates of tobacco and alcohol consumption [19]. However, it is important to note that these lesions can affect individuals of any gender, emphasizing the need for preventive measures for everyone.

Changes in Prevalence: Over time, there have been changes in the prevalence of potentially malignant disorders. While tobacco and alcohol use remains a significant risk factor, some regions have seen a decrease in prevalence due to increased awareness, public health campaigns, and stricter regulations. However, these lesions still pose a significant burden globally, with increasing trends in certain populations [20]. This highlights the ongoing challenges in combating the impact of tobacco and alcohol on oral and maxillofacial health, necessitating continued preventive measures.

Geographical and Demographic Patterns: The epidemiology of potentially malignant disorders exhibits geographical and demographic variations. Regions, such as Southeast Asia and parts of Africa, have higher incidence rates due to specific risk factors prevalent in those areas, such as betel quid chewing. Certain demographic groups, such as older adults and those with low socioeconomic status, may have a higher prevalence due to disparities in healthcare access and lifestyle factors [21]. Understanding these patterns is crucial for implementing targeted prevention and early detection strategies.

Impact of Public Health Interventions: Public health interventions have played a significant role in reducing the burden of potentially malignant disorders. Tobacco control policies, including taxation, cessation programs, and awareness campaigns, have led to a decline in tobacco use and associated lesions in some populations. Similarly, alcohol control measures have shown positive effects [22]. Targeted efforts for high-risk populations, such as screening programs and education initiatives, have facilitated early detection and intervention [23]. By combining population-wide interventions with targeted strategies, further reductions in the incidence and prevalence of these lesions can be achieved [24].

It is crucial of understanding the epidemiology of potentially malignant disorders of the oral and maxillofacial region for effective prevention and management. Age and sex play roles in susceptibility, with older adults and males being more affected, although everyone is at risk. Changes in prevalence, geographical and demographic patterns, and the impact of public health interventions are important considerations. Continued research and collaborative efforts are necessary to address the dynamic nature of these lesions and reduce their global burden on public health.

5. Risk factors, which potentiate the malignant transformation of the potentially malignant disorders of the oral and maxillofacial region

Oral cancers are typically preceded by potentially malignant lesions [25, 26], and 50% precursor lesions converted to oral cancers [27]. Oral cancer exhibits significant variations in its incidence and prevalence across different regions worldwide, highlighting its distinct geographic distribution [28]. Oral cancer is a multifactorial lesion influenced by various factors. These risk factors encompass using tobacco, consuming alcohol, prolonged or excessive UV radiation exposure (generally labial carcinoma), viral infection (e.g., Human papillomavirus (HPV)), fungal infection (e.g., Candida), long-term inflammation, weakened immune system, genetic susceptibility, and dietary habits (Figure 1) [27].

Figure 1.

Risk factors for the malignant transformation of the potentially malignant disorders of the oral and maxillofacial region.

The primary causes of oral cancer identified by various studies are using tobacco and consuming alcohol [26, 27, 29, 30]. The smoke from cigarettes contains various substances, including nicotine, which affects the central nervous system and the gastrointestinal tract, including the oral cavity [27]. Two nicotine metabolites, 4-(Methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) and N′-nitrosonornicotine (NNN), possess carcinogenic properties [27]. These substances bind to the nicotinic acetylcholine receptor, promoting cell growth and creating a favorable environment for tumor development [27]. Smokeless tobacco (SLT) has also been significantly associated with potentially malignant and malignant oral cavity lesions [31]. The International Agency for Research on Cancer (IARC) monograph confirms a substantial link between SLT use and oral cancer. Marijuana smoke contains cannabinoids, immunosuppressants, and a mixture of potentially mutagenic compounds [32]. A case–control study on head and neck squamous cell carcinoma (HNSCC) found a negative correlation between marijuana use and oral cavity cancers [32]. Ethanol, when metabolized into acetaldehyde, a known carcinogen and tumor promoter, contributes to the development of oral cancer through chronic alcohol consumption [27]. Alcohol often contains carcinogenic impurities, such as polycyclic aromatic hydrocarbons and nitrosamines [27]. Although alcohol alone does not have a direct association with cancer progression, it synergistically interacts with tobacco to increase the risk of developing cancer [27]. According to the American Cancer Society, heavy smokers and drinkers face a risk of these cancers approximately 30 times higher than that of nonsmokers and nondrinkers. Betel quid chewing has been identified as a risk factor for oral precancerous lesions [33], particularly playing a major role in the development of submucosal fibrosis [30].

The oral microbiota plays a critical role in maintaining human health by contributing to immune response, nutrient digestion, and carcinogen metabolism [27]. It has been observed that patients with oral cancer often have poor oral hygiene [30]. The human oral cavity is colonized by more than 700 different bacterial species, collectively known as the oral microbiome [27]. Certain viruses such as HPV, EBV, Hepatitis B and C, Helicobacter pylori, as well as bacteria, such as Porphyromonas, Fusobacterium nucleatum, and Prevotella intermedia, have been identified as causes of various types of human cancer [27, 30, 34]. Recent studies found that some bacterial activity on oral epithelial cells, especially bacteria from periopathogenic biofilms, for example, Fusobacterium nucleatum and Porphyromonas gingivalis has the ability to create malignant conditions, which can influence oral oncogenesis [30]. Human papillomavirus (HPV) is a significant risk factor for a specific subset of head and neck squamous cell carcinomas (HNSCC) [27, 35, 36, 37]. Among HNSCC cases, HPV16 is the most prevalent type associated with carcinogenesis, followed by HPV18 [27]. HPV16 carries a higher risk for oropharyngeal squamous cell carcinoma (OPSCC). The early proteins of HPV, namely E6 and E7, play a crucial role in HPV-related OPSCC. E6 inhibits the tumor suppressor protein p53, while E7 binds to pRb (retinoblastoma protein) [27].

Oral cancer can develop as a result of chronic irritation in the mucosa [30]. The release of mediators (e.g., cytokines) is triggered by persistent inflammation, which is linked to chronic irritation and subsequently results in DNA damage due to oxidative stress, contributing in the development of cancer [30]. Chronic mucosal trauma is considered both an initiating factor and a progression promoter in oral cancer. It can either cause lesions on healthy mucosa or exacerbate existing lesions [30]. The risk of oral cancer is increased in individuals who undergo transplantation of allogeneic hematopoietic stem cells, particularly those who develop chronic graft-versus-host disease (GvHD) [38]. For the early detection and management of secondary malignant diseases, it is advisable to closely monitor patients who have chronic graft-versus-host disease (GvHD) on a regular basis. Bullous forms, plaque-like, ulcerative, erythematous erosions, papular, and white reticular striations are the subtype of oral lichen planus (OLP), a chronic inflammatory disease [39]. Those subtypes can affect any person singularly as well combined. OLP promotes some major cancer hallmarks such as immune evasion and tumor-promoting inflammation, and significantly disturbs the immune system [39].

A genetic predisposition plays a significant role in the development of oral squamous cell carcinoma (OSCC), particularly in tongue and buccal mucosa cancers [27]. However, determining the specific genetic or familial disposition for oral cancer is challenging due to the presence of concurrent risk factors, such as smoking and alcohol use [27]. Aberrant methylation has been observed as an early molecular event in the process of oral carcinogenesis [29]. For instance, gene-specific studies have identified inactivation of the p16INK4a gene through CpG methylation as a crucial event in epithelial dysplasia. Additionally, p16INK4a hypermethylation has been associated with loss of heterozygosity (LOH) [29]. Although genetic loss of heterozygosity is considered a better marker for predicting the risk of malignant progression in potentially malignant oral epithelial lesions (PPOEL), it has not yet been integrated into routine clinical practice [25]. Approximately 86 genes, along with the long interspersed elements 1 (LINE1), have been identified to exhibit hypermethylation associated with oral cancer [29]. Most of these 86 hypermethylated genes have been found to be downregulated and exhibit hypermethylation in their promoter regions in OSCCs compared to normal tissue [29]. Some researchers propose that individuals who inherit an impaired ability to metabolize carcinogens or pro-carcinogens and repair DNA damage are more susceptible to developing oral malignancies [27].

The risk of developing oral cancer may be increased due to a low fruit and vegetable diet, coupled with a deficiency in vitamin A. Dietary habits have been consistently linked to the development of several types of cancers [40]. Numerous studies seem to indicate that different food compounds could alter or modify cancer cells [40]. In 2019, a systematic study report published by the World Cancer Research Fund (WCRF) suggested that cancer, for example, oral cancer can be reduced by taking vegetables, fruit, whole grains, and legumes rich diet [41]. Submucosal fibrosis, an oral potentially malignant lesion (OPL), was initially considered idiopathic but is now believed to have a multifactorial etiology. Factors, such as capsaicin, present in chilies, as well as deficiencies in iron, zinc, and vitamins, have been implicated [30]. Consuming very hot foods has been identified as a risk factor for potentially malignant disorders, as a study found a significant difference between patients with oral lichen planus (OLP) and a control group [42]. Oxidative stress and antioxidants are important indicators in oral cancer and potentially malignant disorders as they may predict susceptibility to the development of oral cancer. Normal individuals exhibit differences in the levels of both enzymatic and nonenzymatic antioxidants when compared to patients with oral cancer or oral potentially malignant lesions [43]. Additionally, patients with oral potentially malignant lesions or oral cancer show high level of lipid peroxidation and higher oxidative stress than healthy people [43].

Men have a higher tendency to develop oral cancer compared to women. Out of every 100,000 men, approximately 5.8 men are at risk of being affected by oral cancer, whereas the corresponding number for women is 2.3. The rates of tobacco use and alcohol consumption have recently increased among women, which is significantly changing the current rate of women oral cancer [28]. Due to the difference in lifestyle of men and women, the influence of other risk factors on oral cancer and potentially malignant lesions remains unexplained [44]. There may be some undiscovered factors. There is a fluctuation in women’s oral cancer rate and tumor occurring site, although men have consistency, which lifestyle alone can not explain [44]. Diabetic and underweight individuals were found to be at increased risk of oral potentially malignant lesions [26].

6. Clinico-histological features of the potentially malignant disorders of the oral and maxillofacial region

The clinical presentations and histological features of some of the potentially malignant disorders of the oral and maxillofacial region, which has the potency for the malignant transformation will be discussed in this part. The clinico-histological features are summarized in Table 2.

Potentially malignant disorders of the oral region	Affected area	Clinical presentations	Histological features
Leukoplakia	Any mucous membranes of the oral region.	White or grayish patches in the oral mucosa, well-defined or irregular border. Carcinoma in situ can be found	Hyperkeratosis and epithelial dysplasia can be seen.
Erythroplakia	Buccal and palatal mucous membrane of the oral region, including lower surface of the tongue and floor of the mouth.	Red patches with smooth texture in the oral mucosa, ill-defined border.	Epithelial hyperplasia with cellular atypia and nuclear polymorphism is present. Vascular dilatation, epithelial dysjunction, and basement membrane alteration can be seen.
Oral submucous fibrosis (OSF)	Any mucous membranes of the oral region.	Reduced mouth opening due to progressive mucosal fibrosis, inability to consume hot and spicy food due to burning sensation in the oral mucosa, reduced flexibility of the buccal and labial mucosa	Thinning of epithelial layers, epithelial dysplasia, subepithelial connective tissue fibrosis, hyalinization of the blood vessels, and inflammatory infiltrate may also be seen.
Oral lichen planus (OLP)	Buccal, gingival, and tongue mucosa of the oral region	Wickham’s striae are seen in reticular form. Dysgeusia, burning sensation in the mouth is the common presentations.	Acanthosis (epithelial thickening), hyperkeratosis (epithelial thickening on the outside), and uneven or sawtooth rete ridges (elongation and thickening of the ridges between epithelial rete pegs) are present. Hypergranulosis, subepithelial fibrosis, basal cell degeneration, inflammatory infiltrate, and civatte bodies can be seen.

Table 2.

Clinico-histological features of OPMDs.

6.1 Leukoplakia

6.1.1 Clinical presentations

White or Grayish Patches: The primary characteristic of leukoplakia is the presence of white or grayish patches or plaques on the oral mucosa. These patches can vary in size, shape, and texture [18].

Non-Removability: Leukoplakia patches cannot be scraped off or wiped away. They are firmly attached to the underlying tissues and persist despite gentle manipulation [45].

Irregular Borders: The borders of leukoplakia patches may appear well-defined or irregular [46].

Surface Texture: The surface of the patches can be smooth, rough, or fissured [46].

Thickness: Leukoplakia patches may be flat or slightly raised and can have a thickened consistency [46].

Asymptomatic: In many cases, leukoplakia does not cause any symptoms and is discovered during routine oral examinations. However, some individuals may experience a burning sensation or sensitivity to spicy foods [47].

6.1.2 Histopathological findings

Histopathological examination of leukoplakia is essential for confirming the diagnosis and assessing the degree of dysplasia (abnormal cell changes). The histopathological features of leukoplakia can vary depending on the severity of dysplasia and the specific characteristics of the lesion. Here are the detailed histopathological features commonly observed in leukoplakia [45, 46, 47]:

Hyperkeratosis: Hyperkeratosis refers to an excessive accumulation of keratin, the tough, protective protein found in the outermost layer of the skin. In leukoplakia, there is often hyperkeratosis present in the epithelial layer of the lesion. This thickening of the superficial layer contributes to the characteristic white appearance of leukoplakia.

Acanthosis: Acanthosis refers to the thickening of the epithelial layer due to an increase in the number of cell layers. In leukoplakia, acanthosis can be observed in varying degrees. It indicates cellular proliferation and an alteration in the normal architecture of the oral mucosa.

Epithelial Dysplasia: Dysplasia refers to abnormal changes in the size, shape, and organization of cells within the epithelium. In leukoplakia, varying degrees of dysplasia can be observed, ranging from mild to severe. The presence of dysplasia is an important indicator of the potential for malignant transformation.

1. Mild Dysplasia: Mild dysplasia shows slight cellular abnormalities, including enlarged and hyperchromatic nuclei (increased nuclear size and increased staining intensity). The changes are limited to the lower third of the epithelium.

2. Moderate Dysplasia: Moderate dysplasia exhibits more pronounced cellular changes, extending beyond the lower third of the epithelium but not involving the full thickness.

3. Severe Dysplasia/Carcinoma in situ: Severe dysplasia, also known as carcinoma in situ, demonstrates marked cellular atypia, loss of normal cell differentiation, and involvement of the full thickness of the epithelium. However, there is no invasion into the underlying connective tissue.

Inflammatory Infiltrate: Inflammatory cells, such as lymphocytes and plasma cells, may be present within the underlying connective tissue of leukoplakia. The presence and extent of inflammation can vary and may indicate the body’s response to dysplastic changes or other underlying factors.

It is important to note that the histopathological features of leukoplakia can vary from case to case. Additionally, the degree of dysplasia observed in the histopathological examination plays a significant role in determining the potential for malignant transformation. Regular histopathological evaluation and close clinical monitoring are necessary for appropriate management and treatment decisions in individuals with leukoplakia.

6.2 Erythroplakia

6.2.1 Clinical presentations

Erythroplakia is a potentially malignant oral lesion characterized by a distinct red patch or plaque on the mucous membranes of the oral cavity. It is present as a clinical entity that requires thorough evaluation and monitoring due to its high risk of malignant transformation. Here is a detailed description of the clinical presentation of erythroplakia [45, 46, 47]:

Erythematous Appearance: Erythroplakia appears as a persistent, bright red or deep red patch, or plaque on the oral mucosa. The red coloration is due to various factors, such as increased blood vessel dilation, inflammation, and changes in the epithelial cells.

Smooth or Granular Texture: The surface of erythroplakia can range from smooth and velvety to granular or irregular. It may have a slightly raised or flat appearance.

Non-Removable: Unlike some benign conditions, the red patch of erythroplakia cannot be easily wiped off or scraped away. It is firmly attached to the underlying tissues.

Borders: The borders of erythroplakia lesions are typically irregular or ill-defined. They may blend with the surrounding normal tissue or have a distinct demarcation. The border irregularity is an important characteristic that distinguishes erythroplakia from normal or benign oral mucosa.

Size and Shape: Erythroplakia can range in size from a few millimeters to several centimeters in diameter. The size of the lesion is not indicative of its malignant potential. Erythroplakia can have various shapes, including irregular, oval, or irregularly outlined.

Sites of Involvement: Erythroplakia commonly affects the dorsal surface of the tongue, particularly the posterior and lateral borders. It may also involve the ventral surface or appear as a patch underneath the tongue. The area beneath the tongue, known as the floor of the mouth, is another common site for erythroplakia. Erythroplakia may rarely involve the soft palate at the back of the mouth or the tonsillar area.

Asymptomatic: Erythroplakia is often asymptomatic in its early stages. It may be discovered incidentally during routine dental examinations or self-examinations. As the lesion progresses or becomes more advanced, individuals may experience slight discomfort, including a burning sensation or tenderness at the site of erythroplakia. In some cases, erythroplakia may bleed spontaneously or after minor trauma. However, bleeding is not a consistent feature and may occur in advanced or ulcerated lesions.

6.2.2 Histopathological findings

Histopathological examination of erythroplakia is crucial for assessing its malignant potential and guiding appropriate management. The histopathological characteristics of erythroplakia reveal cellular and tissue changes that indicate its status and progression toward malignancy. Here is a detailed description of the histopathological features commonly observed in erythroplakia [18, 45, 46, 47]:

Epithelial Hyperplasia: Erythroplakia often demonstrates varying degrees of epithelial hyperplasia, characterized by an increase in the number of epithelial layers. The basal layer may show increased cellularity and abnormal cell proliferation. The maturation process of the epithelial cells may be disturbed, leading to a lack of normal differentiation from basal to superficial layers. The epithelium may exhibit a disordered or irregular arrangement of cells with loss of normal cell maturation.

Dysplasia: Dysplastic changes are commonly observed in erythroplakia and indicate a higher risk of malignant transformation. Dysplasia refers to the presence of abnormal cellular and nuclear features within the epithelial layers.

Cellular Atypia: Dysplastic cells exhibit varying degrees of cellular atypia, including increased nuclear-to-cytoplasmic ratio, nuclear pleomorphism (variation in size and shape), hyperchromatism (increased nuclear staining), and increased mitotic activity.

Loss of Architectural Orientation: The dysplastic epithelium may demonstrate loss of normal architectural orientation, with a disorderly arrangement of cells and loss of polarity.

Chronic Inflammation: Inflammatory infiltrates, mainly consisting of lymphocytes and plasma cells, may be present in the connective tissue beneath the dysplastic epithelium. Chronic inflammation is a common feature due to the ongoing tissue reaction to the potentially malignant process.

Vascular Dilatation: Erythroplakia is characterized by a red appearance, indicating increased vascularity. Histopathologically, this is manifested by dilated and congested blood vessels within the lamina propria of epithelial-connective tissue interface.

Epithelial Dysjunction: The junction between the dysplastic epithelium and the underlying connective tissue may show irregularities or epithelial dysjunction. This loss of adhesion between the epithelium and connective tissue is indicative of potential invasive behavior.

Basement Membrane Alterations: Erythroplakia may demonstrate alterations in the basement membrane, which serves as a barrier between the epithelium and connective tissue. These alterations may include thickening, fragmentation, or disruptions in the basement membrane structure.

In advanced cases, erythroplakia may exhibit features of carcinoma in situ, where dysplastic changes involve the full thickness of the epithelium without invasion into the underlying connective tissue. Histopathological examination of erythroplakia helps determine the severity of dysplasia, identify any signs of invasive behavior, and guide appropriate management decisions, such as close monitoring, surgical excision, or other interventions.

6.3 Oral submucous fibrosis (OSF)

6.3.1 Clinical presentations

Clinical manifestations of oral submucous fibrosis (OSF) involve various changes in the oral cavity, including the mucosa, underlying connective tissue, and associated structures. The severity and progression of these manifestations can vary among individuals. Here are the detailed clinical manifestations and oral involvement commonly observed in OSF [18, 45, 46, 47]:

Mucosal Changes: Trismus is one of the hallmark features of OSF. As the fibrosis progresses, the fibrous bands in the oral mucosa cause a gradual reduction in mouth opening. Severe cases may result in significant limitation of jaw movement, making it difficult to eat, speak, or perform oral hygiene procedures. The oral mucosa affected by OSF often appears pale or opaque due to the fibrotic changes and reduced vascularity. The mucosa may have a leathery texture upon palpation. The fibrotic bands in OSF lead to a loss of elasticity in the oral mucosa. The affected tissues feel rigid and less pliable compared to normal mucosa.

Gingival Changes: The gingival tissues may become fibrotic and exhibit a firm leathery consistency. This fibrosis can lead to gingival recession, increased attachment loss, and impaired periodontal health. Fibrotic gingiva may restrict proper tooth brushing and flossing, leading to difficulties in maintaining oral hygiene. This can contribute to the progression of oral diseases, such as dental caries and periodontal disease.

Tongue Involvement: The tongue can be affected by fibrosis in OSF, resulting in reduced tongue mobility and firm consistency. This can lead to difficulties in speaking, swallowing, and articulating certain sounds. The filiform papillae on the dorsum of the tongue may progressively disappear due to fibrotic changes. This can result in a smooth or depapillated appearance of the tongue surface.

Cheek and Lip Changes: The fibrotic changes in OSF can affect the buccal mucosa, leading to a firm, rigid consistency, and reduced flexibility. This can result in difficulty in mouth opening, speaking, and chewing. Fibrosis of the lip mucosa may occur in OSF, causing a tightening or puckering of the lip tissues. This can lead to difficulty in lip movement, affecting functions such as smiling and speaking.

Other Manifestations: Many individuals with OSF experience a burning sensation or discomfort in the affected areas, particularly while consuming spicy or hot foods. In advanced stages of OSF, the fibrotic oral mucosa may become fragile and prone to ulceration. These ulcers can cause pain and increase the risk of secondary infections.

Malignant Transformation: OSF carries a potentially malignant nature, with an increased risk of oral cancer development. Oral leukoplakia, erythroplakia, and other dysplastic changes may be observed in OSF, indicating a higher risk of malignant transformation.

6.3.2 Histopathological findings

Histopathological examination of tissues affected by oral submucous fibrosis (OSF) reveals characteristic findings that help in confirming the diagnosis. Here are the detailed histopathological findings commonly observed in OSF [18, 45, 46, 47]:

Epithelial Changes: The epithelium may show varying degrees of atrophy, characterized by thinning of the epithelial layers. The superficial layers of the epithelium often exhibit hyperkeratosis, with an increased accumulation of keratinized cells. Epithelial dysplasia, characterized by cellular and nuclear atypia, may be observed in some cases of OSF. Dysplasia is considered a premalignant condition and indicates an increased risk of malignant transformation.

Fibrosis and Connective Tissue Changes: One of the key histopathological features of OSF is the presence of dense fibrosis in the subepithelial connective tissue. Fibrosis is mainly composed of collagen fibers and may extend into the deeper connective tissue layers. The collagen fibers in the fibrotic areas appear hyalinized and densely packed. They replace the normal loose connective tissue architecture. Increased numbers of fibroblasts, along with myofibroblasts, can be observed within the fibrotic areas. These cells are responsible for the excessive production and deposition of collagen. Vascular changes, such as hyalinization and obliteration of blood vessels, may be seen in the fibrotic regions. These changes contribute to reduced vascularity and impaired tissue nutrition.

Inflammatory Infiltrate: A chronic inflammatory infiltration composed of lymphocytes, plasma cells, and occasionally, eosinophils, is often present in the subepithelial region. This inflammatory infiltrate is believed to contribute to the fibrogenic process in OSF. Various pro-inflammatory cytokines and growth factors, such as transforming growth factor-beta, interleukin-6, and tumor necrosis factor-alpha, are upregulated in OSF. These molecules play a role in fibroblast activation and collagen synthesis.

Basement Membrane Changes: The basement membrane underlying the epithelium may show thickening and hyalinization. This alteration is believed to be a result of collagen deposition and fibrotic changes.

It is important to note that the severity and extent of these histopathological findings can vary among different individuals and at different stages of OSF. The presence of subepithelial fibrosis, along with epithelial changes and chronic inflammation, is considered essential for the diagnosis of OSF. However, histopathological examination alone may not be sufficient, and a correlation with clinical findings is necessary for accurate diagnosis and management.

6.4 Oral lichen planus (OLP)

Oral Lichen Planus (OLP) is a persistent inflammation of the buccal, lingual, palatal, and gingival mucosa of the oral cavity. It occurs when one’s natural immunity erroneously assaults the healthy epithelium of the oral cavity, causing inflammation and tissue damage. OLP is a kind of lichen planus that can affect the skin, nails, scalp, and genitalia [48, 49].

6.4.1 Clinical presentations

Oral lichen planus (OLP) can manifest in a variety of clinical manifestations that differ from person to person. However, OLP has the following clinical representations [50]:

Reticular Pattern: The reticular form of OLP is the most common, and it is distinguished by a white, lacy, or web-like pattern on the oral mucosa. Wickham’s striae are patterns that can form on the inner lining of the cheeks, tongue, gums, and other regions. The reticular pattern is usually asymptomatic and can be discovered by chance during a standard dental examination.

Erosive/Ulcerative Lesions: OLP can cause erosions or ulcers on the oral mucosa in some circumstances. These areas may appear red, raw, or eroded and may cause pain, burning sensations, or discomfort, especially when eating spicy or acidic meals. The erosive form of OLP might make it difficult to speak or swallow.

Atrophic Lesions: Atrophic OLP is distinguished by oral mucosa thinning and smoothness. The affected areas may appear glossy or shiny, as well as white or erythematous. Atrophic lesions are frequently related with food or drink sensitivities.

Bullous Lesions: In rare situations, OLP may show blister-like lesions known as bullae, which are fluid-filled sacs that can burst and leave erosions or ulcers behind. Bullous OLP can be unpleasant and cause discomfort or problems with oral function.

Plaque-like Lesions: Plaque-like lesions, which are raised areas of the oral mucosa, may appear in some people with OLP. These lesions may be white or gray in appearance and may cause discomfort or irritation.

Oral Symptoms: OLP can cause a burning or stinging sensation, dryness or changed salivary flow, altered taste sensation (dysgeusia), or the sensation of a foreign body in the mouth.

Gingival Involvement: OLP can damage the gingiva (gums) in some situations, causing redness, irritation, and desquamation (peeling) of the gum tissue.

6.4.2 Histopathological findings

The histopathological investigation is critical in diagnosing oral lichen planus (OLP) and distinguishing it from other oral diseases. The primary histopathological findings linked with OLP are as follows [18, 45, 50]:

Epithelial Changes: OLP is characterized by different epithelial alterations in the oral mucosa. These changes may include acanthosis (epithelial thickening), hyperkeratosis (epithelial thickening on the outside), and uneven or sawtooth rete ridges (elongation and thickening of the ridges between epithelial rete pegs).

Basal Cell Degeneration: The presence of basal cell degeneration is one of the defining histological markers of OLP. This is caused by liquefaction degeneration of the basal cell layer, which is characterized by basal cell adhesion loss and disruption of the basal cell layer’s normal architecture.

Inflammatory Infiltrate: OLP is distinguished by a thick and band-like inflammatory infiltrate in the oral mucosa’s underlying connective tissue. T-lymphocytes make up the majority of the infiltration, along with other immune cells such as macrophages and the occasional plasma cell. The inflammatory infiltration is frequently found in the subepithelial region and extends into the connective tissue papillae.

Civatte Bodies: Civatte bodies, also known as colloid bodies or apoptotic bodies, are histological abnormalities that are common in OLP. They are eosinophilic, tiny, spherical formations that reflect degenerated or apoptotic epithelial cells. These entities can be seen distributed throughout the epithelium and the underlying connective tissue.

Hypergranulosis: Hypergranulosis is the thickening and prominence of the granular layer in the epithelium. This feature is seen in OLP and is linked to aberrant keratinization of the oral mucosa.

Subepithelial Fibrosis: Subepithelial fibrosis may be found in more chronic or long-term cases of OLP. This is caused by the deposition of collagen fibers behind the epithelium, resulting in a thicker and fibrotic look.

It is vital to note that the histopathological findings in OLP differ depending on the disease’s stage and severity. Furthermore, because some of these characteristics can be seen in other oral illnesses, histological testing is an important tool for correct diagnosis and differentiation from other disorders.

OLP is often diagnosed based on clinical characteristics along with histological results. For an appropriate diagnosis, a qualified pathologist with experience in oral pathology must assess the biopsy material and link the histological findings with the clinical presentation.

Understanding genetic alterations in the malignant transformation of the potentially malignant disorders of the oral and maxillofacial region.

The transformation of potentially malignant disorders into malignancies is heavily influenced by genetic alterations. These disorders, alternatively termed precursor lesions or intraepithelial neoplasia, encompass abnormal changes in tissue that possess the capacity to progress into cancerous conditions if not appropriately addressed and treated.

Oral cancer typically develops due to cellular alterations. When multiple epithelial cells undergo genetic changes, it is referred to as field cancerization. The initiation of this process is often triggered by oral lesions, which can be categorized as oral potentially malignant disorders. These potentially malignant lesions exhibit genetic instability, resulting in gains or losses of chromosomal material and alterations in nucleotide sequences. Even the border of malignant lesions, some oral cancer specimens show genetic changes. Over the past decade, research has highlighted the crucial role of aberrant DNA methylation in the development of oral cancer. However, oral carcinoma is influenced by various factors related to genetics [51].

During the progression from a potentially malignant lesion to cancer, several genetic alterations can accumulate, leading to uncontrolled cell growth, impaired cell death, and other hallmarks of malignancy. Here are essential insights concerning genetic alterations in the process of turning potentially malignant disorders into malignancies:

1. Oncogenes: Oncogenes are modified versions of normal genes, known as proto-oncogenes, responsible for regulating cell growth and division. Genetic changes, such as mutations, amplifications, or translocations, can transform proto-oncogenes into active oncogenes, leading to continuous activation. This persistent activation drives increased cell proliferation and survival, facilitating the progression of potentially malignant disorders into cancer.

   Oncogenes can be classified in accordance with the functions of their normal association (proto-oncogenes) in the biochemical pathways that controls sequestration and growth. These include in the following table (Table 3) [13]:

2. Growth Factor Receptors: In human tumors, the activation of growth factor receptors involves gene rearrangements, mutations, and overexpression. The development of cancer and stem cells is influenced by specific signaling pathways such as the MAP-Kinase/ERK pathway, the JAK/STAT pathway, the NOTCH signaling pathway, the PI3K/AKT pathway, the Wnt pathway, and the TGF-β pathways.

   Dysregulation of growth factor receptors in oral carcinogenesis occurs due to increased production and autocrine stimulation. Carcinogenesis is characterized by irregular expression of transforming growth factor alpha (TGF-α) and beta (TGF-β) [13].

3. Tumor Suppressor Genes: The transformation of a potentially malignant cell into a malignant one occurs when tumor suppressor genes are inactivated, which is a significant event driving the development of malignancy [13]. These genes play a vital role in regulating cell growth and preventing cancer formation. In potentially malignant disorders, genetic changes can lead to the inactivation or deletion of tumor suppressor genes. Loss-of-function mutations in these genes can disrupt the control mechanisms that inhibit cell division, raising the probability of malignant transformation [39].

4. DNA Repair Genes: DNA repair genes are vital for maintaining genomic stability by repairing DNA damage. Genetic alterations affecting these genes can lead to genomic instability, contributing to the malignant transformation of potentially malignant disorders [52].

5. Chromosomal Abnormalities: Potentially malignant disorders have the potential to experience chromosomal alterations, including deletions, duplications, inversions, or translocations. These changes in the chromosomal structure can lead to disruptions in normal gene function and alter the patterns of gene expression, thereby playing a role in the advancement of cancer [53].

6. Mitochondrial Alteration: Mutations in the mitochondrial genome occur more rapidly than in the nuclear genome in response to oxidative damage and stress. It is speculated that an elevation in the number of copies of mitochondrial DNA serves as a cellular response to counteract dysfunction resulting from oxidative DNA damage. Studies have revealed an augmented copy number of mitochondrial genes in vitiligo, correlating with the severity of histopathological changes [54].

7. Epigenetic Modifications: Epigenetic modifications involve changes in gene expression without altering the DNA sequence. Aberrant epigenetic changes, such as DNA methylation or histone modifications, can silence tumor suppressor genes or activate oncogenes in potentially malignant disorders, thereby facilitating the transformation into malignancy. Epigenetic alterations encompass heritable changes in gene expression that do not involve modifications to the DNA sequence. These changes can occur more frequently than gene mutations and may persist not only throughout the cell’s life but also across subsequent generations [22].

   Gene silencing occurs when high-level expression changes due to altered gene transcription, driven by the influence of epimutations. This alteration disrupts the interplay between activators and suppressors on specific promoters within the context of chromatin. Consequently, disruptions in epigenetic mechanisms lead to the development of carcinomas and other epigenetic disorders by causing inappropriate gene expression [51].

8. DNA Methylation in the Development of Oral Cancer: DNA methylation is a cellular procedure, where the methyl groups are attached with the DNA molecule. Usually, methylation has the ability to alter the activity of a DNA segment except modifying the sequence. Thereafter, DNA methylation can not only influence inappropriate silencing of tumor suppressors but also associated to express oncogenes, which further induce cancer and other disorder. The generation of tumor cells is produced due to chromosome vulnerability through increased mutation rates, which is caused by the repression of proto-oncogenes transcription by either hypomethylation or demethylation. Hypermethylation also expresses the genetic event called loss of heterozygosity that promotes tumor growth. It is also associated with metastatic events and tumor neoangiogenesis [54].

9. DNA Aneuploidy in Cancer: In the context of cancer, genetically stable diploid cells undergo a transformation, giving rise to unstable aneuploid cells. In oral squamous cell carcinoma, the presence of DNA aneuploidy has been extensively studied using advanced techniques, such as flow cytometry and imaging. The findings from these studies reveal the existence of aneuploid tumor populations in numerous cases, underscoring the significance of ploidy status as a crucial prognostic factor [54].

10. Loss of Heterozygosity (LOH): The loss of genomic material from one of the chromosome pairs is called loss of heterozygosity (LOH). LOH in chromosomal regions thought to contain tumor suppressor genes may be associated with malignant developmental processes. LOH in oral potentially malignant disorders and its possible predictive value were recently reviewed. LOHs, particularly those located on chromosome arms 3p and 9p, have been shown to have a greater potential for malignant development of potentially malignant lesions [55].

11. p53: p53 involves many fundamental cell processes such as cell cycle progression, cellular differentiation, DNA repair, and apoptosis. The normal p53 protein has a very short half-life; the quantity in normal cells is extremely small. Mutant p53 protein has a long half-life and can accumulate to detectable levels in cells. This mutant protein is normally inactive, resulting in the loss of the protein’s tumor suppressor function. More than 50% of oral squamous cell carcinomas are p53 positive, and mutations in the p53 gene have been documented [54]. When P53 is mutated, any lesions transform into oral cancers. Leaving apart, the loss of p53 function alters the ability of cells to respond to stress or damage and further promotes genomic instability, and thus promotes malignancy [52].

12. RASSF1 and RASSF2: Both RASSF1 and RASSF2 are members of the Ras family (RASSF) proteins, and both are associated with the Ras/PI3K/AKT pathways. This had already been shown in the investigation of Huang et al. that Ras/PI3K/AKT pathways were turned on in the patient (50%) treated with radiotherapy in corporation with RASSF1A/RASSF2A gene silencing due to methylation. Another study from Imai T et al. investigated that RASSF2 methylated in 26% of OSCC [52, 56].

13. miRNA: Recent study has accounted that MicroRNAs have a significant role in controlling the expression of genes and are inextricably linked to initiating malignancies. Furthermore, miRNA has a variety of crucial participation in cellular processes, for instance, differentiation, proliferation, and apoptosis in both normal and abnormal cells. According to Global miR, investigators have found that overexpression of miR345, miR21, and miR181b have a vital role in malignant transformation. Several investigations have been performed to evaluate the nature of miRNA responsible for carcinoma. For example, Wong TS found that the presence of miR-133a and miR-133B was remarkably declined in OSCC. Diminishing of these levels resulted in the activation of a potential oncogene named pyruvate kinase type M2. In a separate investigation conducted by Kozaki et al., alterations in the expression levels of miR-137 and miR-193a were observed in OSCC (Oral Squamous Cell Carcinoma) cell lines. These changes in miRNA expression were associated with the epigenetic silencing of miRNAs caused by DNA hypermethylation. Such regulatory processes exert a significant influence on the development and progression of oral cancer, contributing to its pathogenesis [51, 57].

14. PTEN: PTEN has a significant role in OSCC pathogenesis, which is named downregulation, usually occurred due to hypermethylation. Although there still is a dilemma regarding the key role of PTEN in OSCC. Here, several studies have performed, such as Squarize et al. documented no aggressive nature of OSCC was found due to PTEN, whereas Shin et al. revealed that the genetic inactivation of PTEN was documented to induce OSCC carcinoma. On the other hand, various research has performed and documented that the abnormal expression of PTEN is directly related to generating and developing OSCC [37, 58].

15. E-Cadherin: Several researches have revealed that the expression of E-cadherin exists in various carcinomas. The significant role of this molecule has also been documented during both tumor generation, as well as development. However, the absence of E-cadherin has a correlation in alterations in cell functions and motility. Furthermore, the loss of its expression is also associated with tissue metastasis. Needless to say, it has found already that lower expression of E-cadherin could result in tremendous aggressive behavior during OSCC [56].

16. DAPK1: DAPK1 (death-associated protein kinase 1) gene maps on chromosome 9q34. Usually, DAPK promotes hypermethylation and causes cancer [51].

17. The impact of immune infiltration: Numerous research studies have shed light on the impact of the immune system in orchestrating adverse changes in OPMDs (Oral Potentially Malignant Disorders). These investigations reveal intriguing findings: there is a prevention of increased infiltration of T-cell CD4+ and CD8+ cells, while the expression of cell processes death protein 1 (PD-1) and programmed cell death ligand (PDL)-1 is evident. Additionally, reduced levels of T cell CD3+ and augmented T helper 1 infiltration play significant roles in the development and progression of cancer associated with OPMDs [52].

18. Microsatellite Instability (MSI): MSI refers to the accumulation of errors in DNA microsatellites, repetitive DNA sequences found throughout the genome. Addition or deletion of microsatellite base pairs, known as microsatellite instability (MSI), is another cytogenetic feature shared by precancerous cells and OSCC [54]. In potentially malignant disorders, MSI can arise due to alterations in DNA mismatch repair genes. MSI can lead to the inactivation of tumor suppressor genes and the activation of oncogenes, contributing to cancer progression [50].

Oncogene category	Functions	Examples	Dysregulation/Mutational impact
Cell surface receptors	Regulate cell signaling and growth	EGFR, FGFR	Overexpression or mutations can lead to uncontrolled cell growth and cancer progression.
Growth factors	Stimulate cell proliferation	TGF, FGF, PDGF	Excessive production can promote cell proliferation, contributing to tumor development.
Inhibitors of apoptosis	Prevent cell death	BCL2	Overexpression can inhibit apoptosis, allowing abnormal cells to survive and grow.
DNA binding nuclear proteins	Regulate gene expression and transcription	MYC, FOS, JUN	Mutations can lead to increased cell proliferation and decreased apoptosis.
Cell cycle proteins	Control cell cycle progression	Cyclins and cyclin-dependent protein kinases	Dysregulation can disrupt cell cycle control, leading to uncontrolled cell division.
Intracellular signal transduction	Transmit signals within the cell	RAS	Mutations can lead to continuous activation of growth-promoting pathways.

Table 3.

Classification of oncogenes with their function and mutational impact.

7. Diagnostic aids in detection of the potentially malignant disorders of the oral and maxillofacial region

Development of cancers and cancer-related death and negative health impacts can be reduced effectively and efficiently by early identification and treatment of premalignant disorders that have a high risk of developing into cancers [29]. This proactive strategy not only helps in detecting cancer at its earliest stages but also allows for interventions that can prevent or delay the progression of these lesions into invasive cancer. Oral lesions are early indications of oral cancer and lesions exhibiting dysplastic characteristics fall under the classification of oral potentially malignant disorders (OPMDs) [22, 59]. These OPMDs include oral leukoplakia, erythroplakia, oral submucous fibrosis (OSF), proliferative verrucous leukoplakia, and oral lichen planus [22, 25, 30], which are considered to carry a significant risk of developing into malignancy [22]. Indeed, conventional oral examination (COE) alone may have limitations when it comes to diagnosing potentially malignant disorders in the oral cavity. However, in recent years, several cutting-edge techniques and advancements in technology have been introduced to overcome these limitations (Figure 2).

Figure 2.

Diagnostic aids for the detection of malignant transformation capacity of the potentially malignant disorders of the oral and maxillofacial region.

Biopsy as a histological examination remains the gold standard for diagnosing oral potentially malignant disorders (OPMDs) [25, 30]. This traditional method involves the surgical removal of a small tissue sample from the suspicious area, which is then examined under a microscope by a pathologist to determine if any abnormal cellular changes or potentially malignant features are present. However, in recent decades, more advanced and less invasive techniques in oral cytology have been proposed as alternative methods for the diagnosis and follow-up of OPMDs. Two notable modern methods are brush biopsy and microbiopsy [30].

At present time, fluorescent technologies are broadly used in potentially malignant diagnosis. Ionic imbalance, abnormal nucleus or high ratios of nucleus/cytoplasm, unnecessary infiltrated inflammation, etc. are the indications of the abnormal mucosal lesion. During the process of examining tissues under chemiluminescent illumination, those abnormal mucosal lesions seen as aceto-white, but healthy normal mucosa display a dark blue color [59]. This difference in appearance is due to variations in how light is scattered back from the tissue between normal mucosa and abnormal lesions. Autofluorescence imaging is another fluorescent technology for potentially malignant lesion diagnosis [30]. This technology uses blue light whose wavelength is 400–460 nm [58]. When blue light is applied to tissues, normal healthy tissue displays apple green fluorescence whose wavelength is 510 nm, while malignant lesions do not show any color (loss of autofluorescence) [59].

Imaging techniques offer additional information to physicians and can assist in planning more effective treatment strategies. In recent years, an innovative category of optical imaging technologies called in vivo microscopy (IVM) has emerged, offering great potential as a diagnostic tool for OPMDs. IVM works by capturing images of minute tissue characteristics through the measurement of tissue optical properties, including reflectance, scattering, absorption, and fluorescence emission. These properties often undergo changes in various disease conditions [25]. The application of IVM has shown promise in the early detection of oral potentially malignant disorders (OPMDs), although the assessment of this method is still in its preliminary stages. Multimodal imaging, optical coherence tomography, reflectance confocal microscopy, and multiphoton microscopy are some examples of IVM.

There are many clinical tissues staining technique for potentially malignant disorders diagnosis; among them toluidine blue, a cationic metachromatic dye is the most common [30]. Toluidine blue is a diagnostic adjunct that can be employed for the early detection of oral squamous cell carcinoma [60, 61]. Toluidine blue has a higher affinity for DNA and RNA, and since malignant lesions contain more DNA and RNA components, they tend to exhibit a greater uptake of the stain [60]. Toluidine blue stained areas of the dysplastic epithelium look royal blue [30]. In a study, the sensitivity of toluidine blue in detecting malignant and potentially malignant lesions was found to be 88.89% [60]. This technique not only aids in the detection of early dysplastic lesions but also assists in determining the appropriate site for biopsy [60]. Furthermore, the method is simple, noninvasive, and can be performed chair-side with a good level of diagnostic accuracy [61]. Vital iodine staining is also effective for detecting potentially malignant and malignant lesions of the oral mucosa [62].

Dysplasia is the most well-established marker but non-obligate precursors of oral squamous cell carcinoma (OSCC) [25]. Phenotypic changes in molecular markers can serve as valuable indicators for evaluating the cancer risk associated with oral potentially malignant disorders (OPMDs). These markers encompass both genetic and protein-based indicators [29]. In the context of OPMD diagnosis, stem cell self-renewal factors can be regarded as biomarkers since there are numerous shared characteristics between stem cells and cancer cells [29]. Some notable protein markers include β-catenin, cyclooxygenase 2 (COX2), c-Met, carbonic anhydrase 9 (CA9), Podoplanin, Ki-67, p16, p53, IMP3, c-Jun, SNAI1 (snail family transcriptional repressor 1), AXIN2 (axin 2), SMAD4 (SMAD family member 4), Notch1, ATM (ATM serine/threonine kinase), yH2AFX, nucleostemin (NS), SOX2 (SRY-box transcription factor 2), ALDH1, and NANOG (Nanoghomeobox), MAGE-A (MAGE family member A), cortactin, FAK (protein tyrosine kinase 2), loss of heterozygosity (LOH), Methyltransferase-Like 3 (METTL3) salivary exosomal microRNAs, etc., all of which have demonstrated potential as risk-predictive markers for OPMDs [29, 63, 64]. The abnormal alterations in the levels of these markers can be indicative of the presence of oral potentially malignant disorders (OPMDs), and the examination of those biomarkers helps to detect oral potentially malignant disorders.

Metabolic phenotypes exhibited notable distinctions between individuals with cancer and those without, indicating a promising avenue for identifying biomarkers associated with various diseases. Metabolic analysis has shown remarkable efficacy in the detection of potentially malignant disorders within the oral cavity [42]. Oral lichen planus (OLP) is classified as an oral potentially malignant disorder. A study utilizing metabolic analysis identified 21 metabolites and eight signaling pathways, which have the potential to serve as biomarkers for OLP [53]. In another study, a biomarker panel composed of Glutamic acid, LysoPE (18:0), and taurine achieved an accuracy of 87.1% in detecting OLP [42]. The researchers employed ultra-performance liquid chromatography-quadrupole/orbitrap high-resolution mass spectrometry (UHPLC-Q-Orbitrap HRMS) for this detection method.

8. Updates of therapeutic strategies in the management of the potentially malignant disorders of the oral and maxillofacial region

The management of the potentially malignant disorders of the oral and maxillofacial regions has improved dramatically in recent years, leading to new therapeutic strategies aimed at improving patient outcomes based on the size and location of it along with the overall health of the individual patient. Here are some updates in therapeutic strategies.

Surgical Excision: Surgical excision is a widely used treatment modality for the management of the potentially malignant disorders of the oropharynx and mandible. The procedure requires complete debridement of the lesion with healthy tissue margins to ensure the removal of the potentially malignant cells. Over the years, advances in surgical techniques have improved patient outcomes by reducing postoperative pain, reducing scarring, and speeding up their recovery [65]. These developments aim to further enhance the precision and outcomes of surgical excision for the potentially malignant disorders.

Minimally invasive surgical techniques have revolutionized the field by reducing the need for multiple incisions and reducing trauma to surrounding tissue. These techniques use small instruments and specialized instruments to remove the lesions accurately while preserving healthy tissue. The benefits of minimally invasive treatment include reduced postoperative pain, shorter hospital stay, faster recovery time, and improved cosmetic outcomes [66]. Such improvements have significantly improved patient experience and overall clinical outcomes.

Robotic-assisted surgery has also emerged as an alternative for the management of the potentially malignant disorders. Robotic systems provide surgeons with improved dexterity, visibility, and control during surgery. This technology allows surgeons to perform complex procedures with precision and accuracy. The use of robots in oral and maxillofacial surgery has shown promising results in terms of improved outcomes and decreased complications [67]. However, it should be noted that robot-assisted surgery may not be suitable for cases all of it, so it will require special training and knowledge.

Navigation systems have become a valuable tool in debridement surgery. These systems use advanced imaging modalities such as computed tomography (CT) scans and three-dimensional (3D) images to provide real-time guidance to surgeons during surgery through the tumor location on the precision of its relationship to the surroundings. The integration of navigation systems into surgical workflows has improved surgical outcomes and patient safety, helping surgeons to make more accurate incisions and to reduce damage to vital physiological markers [68].

Where potentially malignant disorders are extensive or there are deep lymph nodes, extensive surgery may be necessary. These procedures may require the removal of a large portion of the affected area, including the removal of adjacent structures such as bone or tissue. After excision, restorative techniques are often used to restore esthetics and function. Recent advances in reconstructive surgery, such as the use of tissue engineering and regenerative techniques, have made it easier to restore complex defects with displaced consequences effectively. These techniques use biomaterials, grafts, and tissue grafts to replace removed tissue and promote optimal healing and functional recovery [69].

While surgical excision remains an effective treatment strategy for the potentially malignant disorders, it is important to note that it is not without potential risks and complications. The extent of these risks depends on various factors, including the stage and location of the lesion, the surgical skill and experience of the surgeon, and the overall health status of the patient [70]. Potential complications can include bleeding, infection, damage to adjacent structures, and functional impairment, particularly in cases involving more extensive surgical procedures. It is crucial for surgeons to carefully assess each patient and tailor the surgical approach to minimize the risks and optimize treatment outcomes [45].

Photodynamic Therapy (PDT): To reduce the risk of recurrence and progression, adjuvant therapies are often employed in conjunction with surgical excision. These therapies aim to target any remaining abnormal cells or reduce the risk of recurrence. One such approach is the use of photodynamic therapy (PDT) following surgical excision. PDT involves the administration of a photosensitizing agent, which selectively accumulates in precancerous cells. When exposed to a specific wavelength of light, the activated agent generates reactive oxygen species, leading to the destruction of precancerous cells [71]. Combining surgical excision with PDT offers a comprehensive treatment approach that targets both the bulk of the lesion and any remaining abnormal cells, thereby improving treatment outcomes [72].

Laser Surgery: In recent years, the field of oral potentially malignant disorders management has witnessed advancements in nonsurgical treatment options as well. Laser surgery has emerged as a popular alternative to surgical excision. This technique utilizes focused beams of light to precisely target and remove potentially malignant disorders while minimizing damage to surrounding healthy tissues. Laser surgery offers advantages such as improved cosmetic outcomes, reduced postoperative discomfort, and selective destruction of precancerous cells [73]. The choice of laser type and wavelength depends on the characteristics of the lesion and the desired treatment outcome. Furthermore, laser surgery can be combined with photodynamic therapy to enhance its effectiveness through synergistic effects [74].

Topical Medications: Topical medications, such as retinoids and 5-fluorouracil (5-FU), are commonly used in the management of the potentially malignant disorders. Retinoids promote the differentiation of abnormal cells or cause cell death, helping normalize cell growth and reduce the risk of malignant transformation [75, 76]. On the other hand, 5-FU is an antimetabolite medication that interferes with DNA synthesis and inhibits the growth of abnormal cells. These topical medications have demonstrated efficacy in reducing the size and severity of lesions, preventing the development of new lesions, and improving overall outcomes. They are generally well-tolerated, with mild and temporary side effects such as skin irritation and redness [77].

Cryotherapy: Cryotherapy, utilizing extreme cold to freeze and eliminate abnormal cells, is an effective treatment for the potentially malignant disorders such as actinic cheilitis, leukoplakia, and verrucous carcinoma. It offers high cure rates and tissue healing promotion through angiogenesis and collagen formation. Successful outcomes depend on factors, such as lesion characteristics and clinician expertise. While generally safe, cryotherapy may cause side effects such as pain, blistering, and scarring [78]. Therefore, careful patient selection and postoperative care are crucial for minimizing adverse effects and optimizing treatment results. Cryotherapy serves as a valuable therapeutic option in the management of the potentially malignant disorders.

Chemoprevention: Chemoprevention aims to intervene at an early stage and halt or reverse the progression of the potentially malignant disorders, which is another area of advancement in the field. Retinoids have shown promise in preventing the progression of the potentially malignant disorders to oral cancer [79]. Nonsteroidal anti-inflammatory drugs (NSAIDs), such as celecoxib, have demonstrated anti-inflammatory and anticancer properties. Natural compounds, including green tea polyphenols such as epigallocatechin-3-gallate (EGCG), have also been investigated for their chemopreventive effects [80]. While the effectiveness of chemopreventive agents may vary depending on the specific lesion type and stage, they hold potential for reducing the burden of potentially malignant disorders and preventing their transformation into oral cancer.

In conclusion, surgical excision, along with other treatment modalities such as cryotherapy, remains a primary and effective treatment for the potentially malignant disorders of the oral and maxillofacial region. Recent advancements in surgical techniques, imaging, and diagnostics have improved precision, patient experiences, and monitoring. Adjuvant therapies such as photodynamic therapy, combined with surgical excision and cryotherapy, contribute to comprehensive lesion management. Nonsurgical options, such as laser surgery and topical medications, provide alternative approaches with cosmetic benefits. Furthermore, advancements in chemoprevention hold promise in preventing lesion progression. Interdisciplinary collaboration and ongoing research are essential for refining strategies and optimizing outcomes in the management of the potentially malignant disorders.

9. Conclusion

The genetic revelation of the potentially malignant disorders in the oral and maxillofacial region has significant implications for early detection and prevention of oral cancers. This chapter has comprehensively explored various aspects related to the potentially malignant disorders, including their clinical characteristics, epidemiology, risk factors, genetic alterations, diagnostic aids, and therapeutic strategies.

A key finding from this chapter is the critical role of genetic factors in the malignant transformation of the potentially malignant disorders. Mutations in tumor suppressor genes or oncogenes play a pivotal role in driving the progression of these lesions toward malignancy. Understanding these genetic alterations provides valuable insights into the underlying molecular pathways involved in the development of oral cancers, enabling targeted interventions and personalized treatment approaches.

Early detection of the potentially malignant disorders is of utmost importance as they serve as warning signs and precursors to oral cancers. Timely identification and monitoring of these lesions allow healthcare professionals to intervene at an early stage, significantly improving patient outcomes. Genetic markers and molecular biomarkers have emerged as promising tools for facilitating early detection and risk assessment, enabling timely interventions and preventive measures.

Managing the potentially malignant disorders of the oral and maxillofacial region requires a multidisciplinary approach involving collaboration among maxillofacial surgeons, oncologists, pathologists, and other healthcare professionals. This ensures comprehensive evaluation, accurate diagnosis, and tailored treatment plans for each patient. By implementing updated therapeutic strategies, including nonsurgical approaches such as chemoprevention and immunotherapy, and incorporating surgical interventions, when necessary, these lesions can be effectively managed, patient outcomes can be enhanced, and the burden of oral cancers on individuals and society can be reduced.

Continued research and advancements in this field are essential for further enhancing the understanding and optimizing strategies for the prevention and management of the potentially malignant disorders in the oral and maxillofacial region. By leveraging genetic insights and adopting a multidisciplinary approach, significant progress in early detection, prevention, and treatment of oral cancers can be made, ultimately improving patient prognosis and quality of life.