Surface Epithelial-Stromal Tumours
Ovarian cancer typically refers to this family of malignancies, which comprises a large grouping of tumours which arise from the mesothelial lining of the ovary. The extensive sub-types will be considered on separate pages. This group is the most common type of ovarian cancer.
Epidemiology
In Australia ovarian cancer is less common than endometrial cancer but more common than cervical cancer, with about 10 cases per 100,000 women per year. The rate of ovarian cancer is relatively stable. Ovarian cancer is significantly less common in China, Africa and Central America. The average age of diagnosis is 60.
Aetiology
Two protective factors are oral contraceptive use and high parity. There is some evidence of increased rates in women receiving hormone replacement therapy. Ovarian cancer can also be familial, with a 2-fold increase in risk with one first degree relative and 25-fold increase in risk with two first degree relatives. The most important genes are BRCA1 and BRCA2 (BRCA1 is more important). Most familial cases of ovarian cancer can be explained by germline loss of one of these genes. The other important familial disease is Lynch syndrome (HNPCC), which has a much lower association than BRCA1/2.
Pathogenesis
The exact cell of origin for surface epithelial-stromal tumours is not known and may vary for the various subtypes.
Clinical Features
Symptoms of early disease are rarely recognised by women with ovarian cancer, as they usually mimic gastrointestinal complaints. Examination findings are variable, although a pelvic mass or nodules may be palpated (particularly on recto-vaginal examination). Advanced disease with ascites is more clinically apparent. Left supraclavicular nodes may be palpable and pleural effusions are not uncommon.
Ultrasound is the current mainstay of initial imaging investigation, although differentiation between benign and malignant disease is often difficult. Distant staging can be performed with CT. Preoperative staging with MRI is under investigation.
Tumour Types
Common to the surface epithelial-stromal tumours is the concept of malignant, borderline and benign tumours:
- Malignant tumours (adenocarcinoma) typically are large, anaplastic and invade the stroma.
- Borderline tumours are smaller, contain anaplastic features but do not invade through stroma; they may metastasise throughout the peritoneum
- Benign tumours typically form cysts and have no evidence of anaplasia on microscopy.
Serous Tumours
These tumours recapitulate the lining of the fallopian tubes when well differentiated, with columnar and frequently ciliated epithelium. They are sometimes referred to as serous papillary tumours due to their architectural pattern. The malignant serous adenocarcinoma is the most common malignant tumour of the ovary, accounting for 40% of all ovarian malignancies including non-surface epithelial stromal tumours. About 50% of surface epithelial-stromal tumours are serous.
- Serous adenocarcinoma forms gland like or papillary structures; poorly differentiated forms exhibit a solid growth pattern. Psammoma bodies (calcium deposits) are common. Due to common arising on the peritoneal surface of the ovary, these malignancies have a tendency for transcoelaemic spread throughout the peritoneal cavity.
- Borderline tumours form large papillary structures as well as micropapillary structures; they do not show stromal invasion.
- Serous cystadenomas are the benign form of serous tumours, that form unilocular or multiloculated cysts lined by ciliated epithelium
Mucinous Tumours
These tumours consist of cells that contain intracytoplasmic mucin, and often resemble intestinal or endocervical adenocarcinoma. They infrequently involve the surface of the ovary and are therefore more likely to be curable. Mucinous adenocarcinomas are relatively less common (5% of all ovarian malignancies). The benign forms are more common; about 30% of surface epithelial-stromal tumours are mucinous.
- Mucinous adenocarcinoma forms gland like structures; poorly differentiated forms may be solid. Cells contain intracellular mucin.
- Borderline tumours are either intestinal-type or endocervical-type, and are lined by abnormal epithelium that resembles their name.
- Mucinous cystadenomas are the benign form, where cysts are lined by columnar epithelium; the intestinal-type contains goblet cells.
Endometrioid Tumours
These are tumours that resemble the endometrioid tumours of the uterine body. Glandular structures that resemble the normal endometrioid stroma is the norm. A number of cases occur in patients with endometriosis. Endometrioid adenocarcinoma of the ovary accounts for about 20% of malignant ovarian neoplasms.
- Endometrioid adenocarcinoma consists of glandular structures with a stratified, non-mucinous epithelium. Poorly differentiated forms exist
- Carcinosarcoma (malignant Mullerian mixed tumour) may occur in the ovary with poor outcomes
- Endometrial Stromal Sarcoma may also occur in the ovary, with a similarly poor prognosis for high grade lesions
- Borderline endometrioid tumours are rare but do occur, and are lined by endometrial-appearing epithelium with no stromal invasion.
Clear Cell Tumours
Tumours which are made up predominately of clear cells with distinct cytoplasmic membranes.
- Clear cell adenocarcinoma is the most common type, presenting in a similar way to other ovarian tumours but characterised by clear cells in a papillary or tubular pattern.
- Borderline and benign types are rare
Transitional Cell Tumours
These tumours are often referred to as Brenner tumours. Brenner tumours are nests of transitional cells in a fibromatous stroma. Malignant Brenner tumours occur when there is invasive transitional cell carcinoma in conjunction with benign Brenner tumour areas. Transitional cell carcinoma occurs when there is invasive transitional cell carcinoma in the absence of Brenner tumour.
Squamous Cell Carcinoma
Very rare.
Undifferentiated Carcinoma
An uncommon group, these are tumours that can not be classified into one of the other categories by available means. Cells are pleomorphic with no mucin or distinct architectural pattern.
