4 Borderline and Malignant Surface Epithelial – Stromal Tumors of the Ovary

Epithelial ovarian carcinoma (EOC) is the fourth leading cause of cancer mortality among women in western countries. The incidence of newly diagnosed EOC in the US is estimated to be 22,430 cases per year with 15,280 deaths (Jamel A et al., 2006). Surface epithelial-stromal tumors are the most common neoplasms of the ovary. Their origin is likely the epithelium lining the ovarian surface and/or invaginations of this lining into the superficial cortex of the ovary. They occur in women of reproductive age and older. They are usually subclassified as benign, borderline and malignant. Due to the numerous histologic types of ovarian neoplasms, we will limit our discussion to the most common epithelial stromal tumors. We will be discussing the gross appearances, microscopic patterns and differential diagnosis. Based on the 2002 World Health Organization (WHO) classification of ovarian tumors (Tavassoli FA and Devilee P, 2003), Borderline and Malignant Surface-epithelial stromal tumors are classified as:

The papillary structures are yellowish, soft and friable.Grossly, SBT should be differentiated from the hard, stocky, white excrescences that are usually a characteristic of serous cystadenofibroma.SBTs are divided into typical and micropapillary patterns.

Typical SBT
Typical SBT makes up the majority of SBT (90%).Microscopically, the papillae are lined by stratified cuboidal to columnar epithelial cells.These papillae show branching and complex structure.The epithelial cells have high nuclear cytoplasmic ratio (N/C), and the nuclei are hyperchromatic with prominent nucleoli.Mitotic figures are frequently present  Caution should be practiced when one sees what appears to be epithelial proliferation without cytologic atypia, because tangential sectioning of the lining of a benign serous cystadenoma can give the impression of proliferation of the epithelial lining.By definition, SBT lack stromal invasion.This is a major criterion to differentiate SBT from serous adenocarcinoma.Careful gross examination, as well several sections (1 section/1 cm of the tumor diameter) is needed.Finally, invasion of the stalk of the papillae should not be considered as ovarian stromal invasion.

SBT with micropapillary pattern or micropapillary SBT (MSBT)
SBT with micropapillary pattern or micropapillary SBT (MSBT) accounts 5-10% of all SBTs.The significance of this subtype has generated a lot of debate in pathology.Some authors have found a close association between MSBT and invasive implants and urged to call this entity as "micropapillary serous carcinoma".Yet others prefer the terminology of MSBT, avoiding the use of the term of "carcinoma", to minimize the possibility of over treating patients (Chang SJ et al., 2008;Sehdev S et al., 2003).The general agreement on the significance of micropapillary architecture in SBTs is that there is a significant increase in incidence of invasive peritoneal implants (Burks R et al., 1996).Molecular studies show that MSBT has a similar gene expression profile as low-grade serous carcinoma (LGserous carcinoma) and distinct from typical SBT [May T et al., 2010].The underlying genes involved in the pathogenesis of LG-serous carcinoma, and in MBST include mutations in a number of different genes including KRAS and BRAF.Actually, MSBT is the only surface-epithelial stromal tumor with a well defined adenoma-carcinoma sequence, where LG serous is thought to arise in a stepwise fashion from a benign cystadenoma through BST to an invasive LG-serous carcinoma (Kurman RJ et al., 2008).Microscopically, MSBTs shows highly complex micropapillary growth in a filigree pattern, growing in a nonhierarchical fashion from stalk.It has been described as "Medusa head" like appearance.Micropapillae are at least five times as long as they are wide.Micropapillary foci should occupy an area of at least 5 mm, since micropapillary foci of less than 5 mm have no bearing on clinical outcome (Slomovitz MB et al., 2002).

Peritoneal implants
Peritoneal implants are classified into epithelial invasive and non-invasive implants, and desmoplastic invasive and non-invasive implants.Implants are a hetergenous group and various types may coexist, therefore, multiple biopsies of numerous foci of suspicious lesions at the time of surgery and extensive tumor sampling by the pathologist, is the main key to exclude an invasive implant.Epithelial non-invasive implants are characterized by the presence of branching, complex papillae within cystic spaces with no stromal reaction or destruction Desmoplastic non invasive implants are defined by clusters of tumor cells that are present in a loose fibrous stroma.The stroma may have granulation tissue like features with neutrophilic infiltrates and hemorrhage.Differential diagnosis: Implants should be distinguished from benign epithelial inclusions or endosalpingiosis.Inclusions are defined by small glands lined by a single cell layer without atypia.Endosalpingiosis is characterized by a lining typical for tubal epithelium such as ciliated and intercalated cells.

SBT with microinvasion
Microinvasion is defined as single cells or few clusters of cells similar to those seen in the overlying SBT that infiltrate the stroma.One or more foci may be present but none should exceed 10 mm 2 .SBT with microinvasion appears to have no significance on disease outcome, with 10 year survival rate is of 86% (Slomovitz BM et al, 2002).

Implants in a lymph node
Approximately 27% of surgically staged patients with SBT present with lymph node involvement by tumor.The most common lymph nodes involved are the pelvic and paraaortic groups.Recent molecular and morphologic data suggest that although most nodal implants are indeed metastatic from a concurrent ovarian neoplasms, small subsets arises de novo from nodal endosalpingiosis.It has also been suggested that the route of spread from an ovarian SBT to lymph nodes might be via a peritoneal route and not lymphatic.The morphology of the implant is similar to that occurring in the ovary.Lymph node involvement does not adversely impact the overall survival of patients with SBT of the ovary [Fadare O, 2009].The major differential diagnosis is endosalpingiosis and the criteria are cited previously in the text.

Serous carcinoma
Serous adenocarcinoma occurs in women a bit older than women with SBT, with an average age of 56 years.Patients with serous adenocarcinoma often present with advanced stage disease (stage III and IV) at first presentation.Grossly, the tumor varies considerably in size from a few cm to 30 cm.The cut surface may be partially cystic and partially solid or it may be solid with areas of necrosis and hemorrhage   The tumor involves the omentum and create "omental cake" which is characterized by tumoral seeding of the adipose tissue.The cut surface is white, firm and homogenous.

Grading
Grading of surface epithelial stromal tumors is still performed haphazardly with several systems and non-systems used in different institutes and in different research studies.The lack of uniformity in grading has resulted in little consensus as to whether ovarian tumor grade has any significance in predicting disease outcome.The grading systems used most commonly worldwide are the International Federation of Gynecology and Obstetrics (FIGO) system, and the World Health Organization (WHO) system.The FIGO grading system for the ovary is similar to the grading system used in the uterus.It is based on architectural features.The grade depends on the ratio of glandular or papillary structures versus solid tumor growth.Grade 1 is equivalent to <5% solid growth, grade 2 to 5-50% solid growth and grade 3 to =>50% solid growth (International federation of Gynecology & Obstetrics, 1971).In the WHO system, the grade is assessed by both the architectural and cytologic features, without any quantitative values (Tavassoli FA and Devilee P., 2003).The Gynecologic Oncology (GOG) system is the most commonly used system in the United States (Benda JA et al., 1994).It employs a method based on the histologic type.For example, ovarian carcinoma of endometrioid type is graded similarly to the endometrial adenocarcinoma of endometrioid type.Ovarian carcinoma of transitional type is graded similar to transitional cell carcinoma (TCC) of the bladder.Clear cell carcinomas are not graded at all.Silverberg's et al proposed a new grading system similar to that used in breast carcinoma and it depends on architectural features (glandular 1, papillary 2 and solid 3), cytologic atypia (mild 1, moderate 2, severe 3), and mitotic rate (1 0-9 mitosis/10HPF, 2 10-24, 3 >25).A score is given by adding the parameters, a score of 3-5, is grade 1, a score of 6-7 is grade 2, and a score of 8 -9 is grade 3 (Silverberg S, 200).This grading system was confirmed to be reproducible in subsequent studies (Ishioka SI et al., 2002).Another study from MD Anderson cancer center group suggested adopting a twotier system that is based primarily on the assessment of nuclear atypia (uniformity vs. pleomorphism) in the worst area of the tumor (Malpica A et al., 2004).The tumor is graded into low grade and high grade.A few years after its introduction, the authors confirmed its reproducibility and urged its use to facilitate the clinical trials and protocols (Malpica A et al., 2007).

Mucinous borderline tumors
Mucinous borderline tumors (MBT) (mucinous tumors of low malignant potential) as defined by the WHO, are tumors exhibiting an epithelial proliferation of mucinous type cells greater than that seen in their benign counterparts but without evidence of stromal invasion.MBT can be of intestinal type or endocervical-like type.

Mucinous borderline tumors of intestinal type
The intestinal type tumors are the most common type of MBTs, accounting for 85-90% of cases.They are not associated with peritoneal implants or lymph node involvement.Similar to low-grade serous tumors, intestinal type MBTs are thought to arise from a cystadenoma and to progress to carcinoma, following the adenoma-carcinoma sequence model.Grossly, they are usually a very large unicystic or multicystic mass filled with mucoid-gelatinous material

Mucinous borderline tumors of endocervical type
The endocervical type tumors are a less common and make up 10-15% of MBTs.They are usually smaller in size than their intestinal type counterparts and they are commonly bilateral (40%).They are thought to arise from endometriosis.Microscopically, the epithelial cells lining the cyst wall contain intracytoplasmic mucin, resembling endocervical cells.

Mucinous tumors with mural nodules
Mucinous tumors of the ovary, whether benign, borderline or malignant, may contain one or more nodules.These nodules are morphologically different than the overlying mucinous neoplasm.Grossly, nodules are yellow, pink with areas of hemorrhage and necrosis Microscopically, the mural nodules may be malignant (anaplastic, sarcoma or carcinosarcoma) or benign (sarcoma-like).It is important to distinguish between benign and malignant mural nodules, because benign mural nodules are of no prognostic significance.Immunohistochemistry is a very helpful tool for this purpose.Sarcoma-like nodules are composed of a heterogenous cell population of cells including spindle cells, giant cells, mononuclear cells and inflammatory cells.The cells of the sarcoma-like nodules are negative or very weakly positive for cytokeratin Fig3.1.3.b.   Lastly Sarcoma nodules exhibit a variety of patterns such as fibrosarcoma, rhabdomyosarcoma and undifferentiated sarcoma.

Mucinous adenocarcinoma
Mucinous adenocarcinomas (MAC) are very large tumors; many are 15 to 30 cm in diameter and weigh as much as 4 kgs.The cut surface can be cystic or solid and the content is composed of gelatinous, mucoid material    This classification is prognostically significant with 5-year survival rates of 84% for DPAM and 6.7% for PMCA (Ronnett BM et al, 2001).PP may originate from an ovarian primary or from an appendiceal primary.An appendectomy is necessary in those circumstances.Grossly, the appendix shows a dilated lumen filled with mucinous material.Histologically, depending upon the cytologic atypia, the appendiceal tumor may be a mucinous adenocarcinoma or a mucinous tumor of low malignant potential  In many cases, the appendix is encased by a very large mucinous mass, and histologically, the appendix is replaced by tumor, rendering the diagnosis of appendiceal primary very difficult.Not so long ago, there was a considerable controversy about the origin of mucin in PP, in women with concomitant mucinous tumors of the appendix and the ovaries.Recent immunohistochemical, molecular, and genetic evidence supports the appendix as the primary tumor and secondary involvement of the ovary (Ronnet BM et al, 2004) In difficult cases, immunohistochemistry study including cytokeratin 7 (CK7), cytokeration 20 (CK20) and CDX2 are useful to discriminate between primary appendix from primary ovarian mucinous tumors.At first CDX2 seemed to be a promising marker and its positivity was found to be very specific for lower gastrointestinal carcinomas but as more studies have been published, more cases of ovarian mucinous tumors have been found to be positive for CDX2 rendering its use of little value.On the other hand CK7/CK20 is more useful, as ovarian mucinous tumor are CK7+/CK20+ and appendiceal/ colon tumors are CK7-/CK20+.Thus, CK7/CK20 is the most useful and reliable combination in distinguishing appendiceal versus ovarian primary (Chu P et al., 2000;Kaimaktchiev et al., 2004).

Endometrioid adenocarcinoma
Endometrioid adenocarcinoma (EAC) account for 10-20% of ovarian carcinomas.They occur in postmenauposal women, with average age of 56 years.The frequent association with endometriosis and endometrioid adenocarcinoma of the endometrium suggested that some EAC of the ovary might have the same risk factors as those occurring in the endometrium.In contrary to serous carcinomas, about half of EAC cases present as early stage disease (stage I and II).They are bilateral in 20% of cases.Microscopically, these tumors are usually well differentiated tumors (grade I).The tumor is microscopically very similar to those occurring in the endometrium, where back to back glands with no intervening stroma and squamous differentiation in the form of squamous morules and keratin pearls are present.Rare examples of mucin-rich, secretory, ciliated, and oxyphilic types have been described.Occasionally the tumor may resemble granulosa cell tumor, with the cells arranged in ribbons, and small glands, creating the illusion of Call-Exner bodies.Also, rare cases exhibit tubular glands resembling a Sertoli-Leydig cell tumor.In both cases alpha-inhibin is excellent marker to differentiate between EAC and sex-cord tumors, where it is negative in EAC of the ovary and it is positive in sex-cord stromal tumors such as Sertoli-Leydig tumors and granulosa cell tumors

Clear cell carcinoma
Clear cell carcinomas (CCC) represent 6% of surface-epithelial tumors.They occur in postmenopausal women, with a mean age of 57 years.CCC of the ovary has a few notable characteristics 1-they are almost always unilateral, 2-they are admixed with endometrioid type adenocarcinoma in 20-25% of cases, 3-they are often accompanied by endometriosis of the same ovary, 4-they may be associated with paraneoplastic hypercalcemia and 5-they have frequent mutations of ARID1A and PIK3CA genes     Metastatic RCC to the ovary, though rare, creates a major diagnostic challenge, when CCC of the ovary is of clear cell type.It is almost impossible to differentiate the two based solely on morphology.Therefore, IHC is helpful as RCC is usually negative for CK7 and positive for CD10 and CCC of the ovary is typically positive for CK7 and negative for CD10.In addition, correlation with radiologic findings is necessary to rule out metastatic RCC (Mittal K et al, 2008).

Transitional cell carcinoma and malignant Brenner tumors
The group of transitional cell tumors includes benign Brenner tumors, borderline and malignant Brenner tumors, and transitional cell carcinoma.By definition, transitional cell carcinoma of the ovary (TCC-O) and malignant Brenner tumors are composed of epithelial cells morphologically resembling urothelium.TCC-O is the least common surface epithelial tumor of the ovary, accounting 1-2% of all ovarian tumors.It may sometimes be associated with germ cell tumors.They are bilateral in 15% of the cases.Grossly they are cystic with intracystic papillary projections  Before the diagnosis of primary squamous cell carcinoma of the ovary is made, metastatic SCC from the cervix should be excluded.In addition, primary SCCs of the ovary should be distinguished from endometrioid adenocarcinoma with extensive squamous differentiation.Thus, extensive sampling is recommended.Cases of primary SCCs of the ovary frequently have spread beyond ovary at the time of presentation, leading to poor prognosis.

Ovarian carcinoma after neoadjuvant therapy
Traditionally, advanced stage ovarian carcinoma is treated by debulking surgery followed by chemotherapy.In some circumstances, neoadjuvant chemotherapy followed by debulking surgery may be done.Neoadjuvant chemotherapy is increasingly being used in the management of patients with advanced ovarian cancer and pathologists should be aware of the morphologic changes in ovarian cancer after neoadjuvant chemotherapy.For the inexperienced or those with no knowledge of the patients' history, treated tumors may be mistaken for metastatic carcinoma from breast primary or other sites.The morphologic   The immunohistochemistry profile is similar to that of native untreated tumors.Ck7, CA125, WT1, ER, p53 and p16 may be of value in identifying residual tumor cells [Miller K et al., 2008].

Conclusion
Ovarian tumors are often complex and heterogenous in nature.In this book chapter we limited our discussion to the most common ovarian tumors in adult women.This is a concise histological description of these tumors that clinicians will find useful in their daily practice.

Fig. 2
Fig. 2.1.b.BST.In another case, instead of polypoid excrescences on the outer surface of the ovary, papillary projections are seen within the cyst lumen of the ovary.
Fig. 2.1.1.a.BST: At the low magnification, the tumor is composed of papillary projections.

Fig. 2
Fig. 2.1.1.b.BST: At higher magnification, the papillae are lined by epithelial cells exhibiting severe pleomorphism with moderate to severe atypia and with high nuclear/cytoplasmic ratio.They have big round nuclei and prominent nucleoli.

Fig. 2
Fig. 2.1.2.a.Micropapillary SBT: Microscopic examination shows highly complex micropapillary growth in a filigree pattern, which is defined by a growth in a nonhierarchical fashion from fibrous stalk forming what we say "Medusa head' like appearance.

Fig. 2
Fig. 2.1.2.b.Micropapillary SBT: The micropapillae are at least five times as long as they are wide.
Fig. 2.1.3.a.Non-invasive peritoneal implant: The implant is defined by papillary structure in a space like structure with no evidence of invasion or destruction of the ovarian stroma.

Fig. 2
Fig. 2.2.a.Serous adenocarcinoma: the ovarian mass is solid with few cystic areas.The cut surface is firm, white with areas of necrosis and hemorrhage.

Fig. 2
Fig. 2.2.b.Omentum: The tumor involves the omentum and create "omental cake" which is characterized by tumoral seeding of the adipose tissue.The cut surface is white, firm and homogenous.
Fig. 2.2.1.a.Low grade serous carcinoma: The tumor has papillary features.The neoplastic cells have mild to moderate atypia and rare mitotic figures.

Fig. 2
Fig. 2.2.1.b. High grade serous carcinoma: The tumor cells are arranged in solid sheets with very rare foci of papillary architecture.The cells exhibit severe atypia and frequent mitotic figures.

Fig. 3
Fig. 3.1.1.a.Mucinous borderline tumor (MBT): The cut surface of the ovarian mass shows multiple cysts filled with gelatinous material.However in some areas the wall of the cyst seemed to be thickened.Histologically, the lining of the cyst is composed of stratified lining of epithelial cells having high N/C ratio and prominent nucleoli Fig 3.1.1.b,c.Goblet cells and Paneth cells are present.No stromal invasion is seen.
Fig. 3.1.1.c.Higher magnification showed that the glands are lined by mucin secreting cells exhibiting moderate to severe atypia, big nuclei and prominent nucleoli.In some areas, the cytoplasm shows mucin depletion.Mitotic figures are frequently present.
Fig. 3.1.3.a.Mural nodules: Mural nodules are grossly characterized by a well defined mass within the wall of the cyst.The cut surface is often hemorrhagic.

Fig. 3
Fig. 3.1.3.b.Sarcoma-like nodules: They are composed of heterogenous cell population including spindle cells, giant cells, mononuclear cells and inflammatory cells.Anaplastic sarcoma mural nodules are composed of diffuse sheets of spindled or large rhabdoid-looking cells with abundant eosinophilic cytoplasm and prominent nucleoli fig 3.1.3.c,d.These cells are usually strongly positive for cytokeratin fig 3.1.3.e.

Fig. 3
Fig. 3.2.a.Mucinous cystadenocarcinomas: Grossly, they are characterized by partially cystic and partially solid mass.The cysts content is composed of gelatinous material.These tumors are defined by invasion and adequate sampling is a key factor to document invasion process.Numerous sections (2 to 3 sections /1cm of tumor diameter) are required.Invasion can be defined as infiltration of ovarian stroma by neoplastic cells arranged in nests or as single cells with a stromal desmoplastic reaction Fig 3.2.b,c.

Fig. 3
Fig. 3.2.c.Mucinous adenocarcinoma: These glands are cytologically malignant with severe atypia, large nucleoli, loss of cytoplasmic mucin and numerous mitosis.However, one needs not to see typical stromal invasion with desmoplastic reaction to diagnose MAC, because invasion can also be defined as neoplastic glands which are back to back with no intervening stroma Fig 3.2d.Similar to MBTs, the epithelial lining in MAC can be of intestinal or endocervical type.MAC should be distinguished from metastatic adenocarcinoma from colonic origin.Metastatic colonic carcinomas are usually bilateral.Morphologically, they are characterized by glandular proliferation with abundant dirty necrosis and nuclear debris within amorphous necrotic tissue.The glands are lined by stratified cells with prominent atypia and mitosis Fig 3.2.e

Fig. 3
Fig. 3.2.e.Metastatic colon carcinoma: It is characterized by large glands with center "dirty" necrosis and nuclear debris within amorphous necrotic tissue.

Fig. 3
Fig. 3.3.b.Peritoneal adenocarcinomatosis: It is characterized by pool of mucin and clusters of malignant cells with signet-ring features.

Fig. 3
Fig. 3.3.d.Appendiceal mucinous tumor: The appendiceal mucosa shows proliferation of mucin-secreting cells that they are not frankly malignant.Due to the absence of glandular cribriform and submucosal invasion, this lesion is classified as mucinous tumor of low malignant potential.
Fig. 4.1.a.Endometrioid adenocarcinoma (EAC): The morphologic features of this tumor are very similar to those occurring in the endometrium where back to back glands with no intervening stroma.
Fig. 5.a.Clear cell carcinoma (CCC): low magnification shows proliferation of neoplastic cells in form of solid sheets and papillary patterns.

Fig. 5
Fig. 5.b.CCC: The cells have a clear cytoplasm, and eccentrically located round nuclei.

Fig. 5
Fig. 5.c.CCC: some cells contain inspissated secretion that is mucicarmine positive creating a targetoid appearance.Due to these various patterns, CCC can be mistaken for germ cell tumors including dysgerminoma, yolk sac tumors, endometrioid adenocarcinoma with secretory changes, and with metastatic renal cell carcinoma (RCC) Fig 5.d,e.

Fig. 5
Fig. 5.d.Yolk sac tumor: The tumor is arranged in a loose stroma with small cystic structures.

Fig. 5
Fig. 5.e.Yolk sac tumor: The tumor cells have abundant eosinophilic cytoplasm and contain hyaline bodies.Alpha-fetoprotein (AFP), placenta alkaline phosphatse (PLAP), cytokeratins and epithelial membrane antigen (EMA) are helpful immunohistochemistry stains to distinguish CCC from germ cell tumors.In germ cell tumors, AFP and PLAP are positive and cytokeratin and EMA are negative, while CCC cells are negative for AFP and PLAP and positive for cytokeratin and EMA (Mittal k et al 2008).
Fig. 6.a.Transitional cell carcinoma of the ovary (TCC-O): The mass is mostly composed of one large cystic where a large vegetating tumoral mass protrudes in the lumen.TCC-O can be already widespread disease at the time of diagnosis, however, malignant Brenner tumors are usually stage I disease at first presentation.Histologically, TCC-O and malignant Brenner tumors resemble TCC occurring in the urinary tract.They are composed of papillary projections protruding into a cystic lumen, lined by multilayered malignant transitional epithelium Fig 6.b.c.

Fig. 6
Fig. 6.b.TCC-O: The tumor is composed of broad undulating macropapillae with smooth borders.
changes seen in response to neoadjuvant chemotherapy include small groups or single tumor cells in a densely fibrotic stroma Fig 8.a.The tumor cells are characterized by nuclear and cytoplasmic alteration making the grading and sometimes the tumor typing impossible and inaccurate.Nuclear changes include nuclear enlargement, hyperchromasia, irregular nuclear outlines and chromatin smudging.Cytoplasmic alterations include eosinopholic cytoplasm, vacuolation and foamy cell changes Fig 8.b.The stroma may have pronounced fibrosis, inflammation, foamy histiocytic infiltrates, hemosiderin deposits, necrosis, calcification and numerous free psammoma bodies (McCluggage WG et al., 2002; Chew I et al., 2009).

Fig. 8
Fig. 8.a.Ovarian carcinoma after neoadjuvant therapy: The tumor presents extensive areas of fibrosis with few areas of remaining viable tumor cells.

Fig. 8
Fig. 8.b.Ovarian carcinoma after neoadjuvant therapy The nuclear changes seen including nuclear enlargement, hyperchromasia, irregular nuclear outlines and chromatin smudging.