Mucinous

Borderline/LMP
Borderline/LMP tumours are characterised by epithelial multilayering of more than 4 cell layers, and less than 4 mitoses per 10 high-power field, mild nuclear atypia, increased nuclear/cytoplasmic ratio, slight-to-complex branching of epithelial papillae and pseudopapillae, epithelial budding and cell detachment into the lumen and no destructive stromal invasion. Borderline mucinous tumours have similar gross morphology to their benign counterparts, cysts with smooth surfaces. The epithelial layer is characterised by stratification of 2-3 layers, nuclear atypia, enlarged nuclei and mitotic figures. Histological examples of borderline mucinous tumours can be found at:
http://pathweb.uchc.edu/eAtlas/GYN/1934.htm
http://pathweb.uchc.edu/eAtlas/GYN/1935b.htm
Approximately 25% of borderline tumours show cell proliferations on the outer surface only. Of these, 90% develop peritoneal implants, which can be invasive or non-invasive. Both have a similar appearance, glandular or papillary proliferations with cell detachments, sometimes Psammoma bodies, cellular atypia and desmoplastic fibrosis. However, epithelial cells infiltrate the stroma in the invasive implants.

Brenner tumours
Brenner tumours are solid or cystic, yellow-tan colour and firm upon gross examination. Histological examination of Brenner tumour reveals epithelial nests or cysts of cells, resembling urothelium, separated by a cellular, fibrous stroma (composed of spindle-like cells). The nuclei are relatively uniform, lacking pleomorphism, hyperchromasia or macronucleoli, and mitoses are not identified. There is a moderate amount of eosinophilic cytoplasm. Examples of Brenner tumours can be viewed at:
http://pathweb.uchc.edu/eAtlas/GYN/1941b.htm
http://pathweb.uchc.edu/eAtlas/GYN/1942.htm
http://pathweb.uchc.edu/eAtlas/GYN/1943.htm
http://pathweb.uchc.edu/eAtlas/GYN/1299.htm
http://pathweb.uchc.edu/eAtlas/GYN/1300.htm
http://pathweb.uchc.edu/eAtlas/GYN/1301.htm
http://pathweb.uchc.edu/eAtlas/GYN/1302.htm

Clear Cell Carcinoma
Clear cell carcinoma accounts for 5-12% of ovarian adenocarcinomas. The gross appearance of clear cell carcinoma shows a smooth, lobulated external surface. These tumours are usually solid and firm, but can be cystic. They have a yellow-tan colour. Microscopic examination reveals cells arranged in tubules, nests or cysts, with clear, glycogen rich cytoplasm, sharply demarcated cell borders, and hyperchromatic, pleomorphic nuclei. Hobnail cells with nucleus standing on a stalk of cytoplasm are visible microscopically. Examples of clear cell carcinoma can be found using the following weblinks:
http://pathweb.uchc.edu/eAtlas/GYN/1937.htm
http://pathweb.uchc.edu/eAtlas/GYN/1938.htm
http://pathweb.uchc.edu/eAtlas/GYN/1939.htm
http://pathweb.uchc.edu/eAtlas/GYN/1940.htm
http://pathweb.uchc.edu/eAtlas/GYN/1049.htm
http://pathweb.uchc.edu/eAtlas/GYN/1050.htm
http://pathweb.uchc.edu/eAtlas/GYN/1051.htm
http://pathweb.uchc.edu/eAtlas/GYN/1052.htm
http://pathweb.uchc.edu/eAtlas/GYN/1053.htm

Endometrioid Carcinoma
Endometrioid carcinomas are solid, white, firm tumours with smooth or irregular surfaces. They may contain a cystic component and have areas of necrosis and haemorrhage. Histological analysis reveals glands, or glands mixed with solid areas, round-oval vesicular, clear nuclei with prominent nucleoli. Endometrioid carcinoma is indistinguishable from endometrial carcinoma. An example of endometrioid carcinoma can be found at:
http://pathweb.uchc.edu/eAtlas/GYN/437.htm

Mixed Mesodermal
The gross appearance of mixed mesodermal ovarian tumours are exemplified in the following weblinks:
http://pathweb.uchc.edu/eAtlas/GYN/134.htm
http://pathweb.uchc.edu/eAtlas/GYN/135.htm
http://pathweb.uchc.edu/eAtlas/GYN/136.htm
They are usually large variegated lesions with necrotic and haemorrhagic regions, and may have adhesions. Microscopic examination reveals serous or endometrioid epithelial component displaying squamous differentiation. Stroma may comprise spindle cell or soft tissue differentiation including cartilage, skeletal muscle or smooth muscle.

The presence of cytogenetic aberrations common to all subtypes suggests these tumours develop by progression.

The main conclusions from cytogenetic investigations of ovarian epithelial tumours are as follows:

CGH findings of Sporadic and Hereditary Ovarian Carcinoma

CGH profiles were compared from sporadic and hereditary (3 BRCA1 and 1 BRCA2 mutation carriers) ovarian cancers. The commonest imbalance included amplification of 8q22.1-qter (66.6%), 1q22-32.1 (41.1%), 3q (75%) and 10p (33.2 %), and deletion of 9q (41.6%) and 16q21-q24 (33.3%). Deletions of 9q were found in all 3 BRCA1 carriers and 2/8 sporadic tumours, and deletions of 19 were found in 2/3 BRCA1 carriers and none of the sporadic cases. These findings suggest preferential somatic losses of chromosome 9 and 19 in BRCA1 mutation carriers. In contrast, another study identified extensive similarity by CGH between sporadic and hereditary ovarian carcinomas, except for 2q24-q32. CGH analysis of a further 36 hereditary tumours found the majority of imbalances to be similar to that of sporadic tumours (Gains: 8q23-qter, 3q26.3-qter, 11q22, 2q31-32; losses: 8p21-pter, 16q22-qter, 22q13, 12q24, 15q11-15, 17p12-13, Xp21-22, 20q13, 15q24-25, 18q21). However some imbalances were identified that were specific to hereditary tumours, including deletions of 15q11-15, 15q24-25, 8p21-pter, 22q13 and 12q24, and gains of 11q22, 13q22 and 17q23-35. Deletions of 15q11-15 and 15q24-25 were found in 16/36 and 12/36 cases respectively which implicated hRAD51 and other tumour suppressor genes in these loci in the genesis of hereditary ovarian cancer.

All 3 patterns of familial ovarian cancer are consistent with autosomal-dominant transmission of one or more genes responsible for the development of >1 cancers, with incomplete penetrance and variable expression. The age of diagnosis of hereditary epithelial ovarian cancer is approximately 10 years earlier than its sporadic counterpart.

Breast-Ovarian Syndrome
Of the about 10% of ovarian epithelial cancers thought to have a hereditary component, 90% are associated with breast-ovarian syndrome. This syndrome is associated with two genes, BRCA1 at 17q21, and BRCA2 at 13q12.3 (see below), which are involved in DNA repair and transcription regulation. Mutations are distributed throughout the entire coding regions of BRCA1 and BRCA2, and most result in truncation of the protein. Germline mutations in BRCA1 account for about 80% of hereditary breast-ovarian cancers. Germline mutations of BRCA2 account for about 10-35% of familial ovarian cancers. BRCA1 is associated with a 26% cumulative risk for ovarian cancer for most mutation carriers, and a much higher risk, 85%, in a small subset. Women with a germline BRCA1 mutation have an about 40% risk of developing ovarian cancer by 70 years of age. BRCA2 increases susceptibility to a smaller degree. The lifetime risk for developing ovarian cancer in BRCA2 mutation carriers is 27%. However the risks of developing ovarian cancer associated with germline mutations of BRCA1 and BRCA2 vary according to the population studied. A study by revealed a lifetime risk of ovarian cancer of 40-60% for BRCA1 mutation carriers, whereas another one found a 25-30% risk for BRCA1 mutation carriers. Approximately 1/4000 in the general population has a mutation of BRCA1, although some populations have much higher incidences, for example the Ashkenazi Jews. Patients with breast cancer who had BRCA1 or BRCA2 mutations had a tenfold increased risk of developing ovarian cancer.

The variable penetrance of BRCA1 suggests that other genetic and non-genetic factors contribute to the pathogenesis in these individuals. One such modifier is a VNTR polymorphism, 1-kb downstream of HRAS. BRCA1 carriers with rare alleles of the VNTR had an 2.11 increased risk of developing ovarian cancer compared with the common alleles (p=0.015).

about 50% of familial ovarian cancers are not associated with germline BRCA1 or BRCA2 mutations. Linkage and LOH analysis has suggested a susceptibility gene for familial ovarian cancer at 3p22-p25. LOH of 3p33-p25 is higher (52%) in non-BRCA1/BRCA2 familial ovarian cancers than in the BRCA1 (29.7%) group.

HNPCC
Mutations of the mismatch repair genes (MMR) including MLH1, MSH2 and MSH6 are present in HNPCC syndrome (Lynch 2 Syndrome). This represents the second most common type of ovarian cancer with a hereditary component.

Site-Specific Ovarian Cancer Syndrome
The least common of the familial ovarian cancers is the site-specific ovarian cancer syndrome, in which ovarian cancer is the dominant cancer. It has been suggested that site-specific ovarian cancer is a variant of breast-ovarian syndrome attributable to mutation in either BRCA1 or BRCA2, and not a distinct clinical entity.

Early onset ovarian carcinoma (

The pattern of allelic loss differs according to the histological subtypes of epithelial ovarian cancer. Clear cell adenocarcinoma predominantly demonstrates LOH of 1p, 19p and 11q. Serous adenocarcinoma demonstrates allelic losses in >50% of cases of 1p, 4p, 5q, 6p, 8p, 9q, 12q, 13q, 15q, 16p, 17p, 17q, 18p, 18q, 19p, 20p and Xp. Endometrioid adenocarcinoma frequently demonstrated LOH of 7p, and mucinous adenocarcinoma demonstrated recurrent LOH at 17p13.1. LOH analysis using RFLP markers in 6q24-q27 demonstrated allelic loss at a few or all loci in 17/33 ovarian serous tumours, 1/15 ovarian mucinous tumours, and 2/12 ovarian clear cell tumours. Allelic loss of 1p31 has been found in about 40% of ovarian carcinomas, where the maternally imprinted tumour suppressor gene ARH1(NOEY2) resides. Approximately 1/3 of epithelial ovarian tumours of all stages demonstrate LOH of 9p. 69% of 78 ovarian epithelial tumours displayed LOH of 17p13.1 where TP53 is located. Allelic loss at 10q23.3 flanking PTEN and within PTGN have been found in 45% of ovarian epithelial cancers (n=68). Loss of PTEN expression was associated with elevated phosphorylated AKT levels. No microsatellite instability (MSI) was apparent among the 23 benign cystadenomas and 31 LMP ovarian tumours examined using 69 microsatellite markers. Thus these findings suggest MSI is not a pathogenic mechanism in the development of LMP tumours, and abnormalities of the DNA mismatch repair mechanisms are not involved. In contrast, about one-third of endometrioid carcinomas and up to 40% of serous LMP tumours display MSI, although in serous LMP tumours the MSI is low level.

LOH of 3p14.2, 11p15.5, 11q23.3, 11q24, 16q24.3 and 17p13.1 are more frequent in advanced than lower stage tumours. LOH of 3p14.2 correlated with tumour metastasis, whereas LOH at 11p15.5 and 11q23.3 were associated with reduced survival. LOH of 11q22.3 was associated with reduced survival and a serous histology, meanwhile LOH of 11q24-25 correlated with a higher tumour stage, serous histology, presence of residual tumour, but not with survival. LOH of 1p36 is associated with poor histological grade.

Homozygous deletions or intragenic mutations of CDKN2A (p16INK4A) are also found in ovarian epithelial tumours. CDKN2A encodes an inhibitory protein of cyclin-dependent kinase 4. The CDKN2A complex blocks phosphorylation of the Retinoblastoma (RB) protein. Phosphorylation of the RB protein is a prerequisite for cells to enter the S phase of the cell cycle. Thus CDKN2A is a negative regulator of the cell cycle.

Reduced expression of RNASET2 (RNASE6PL), located at 6q27, was found in 30% of ovarian cancers. Transfection of RNASET2 cDNA into ovarian cancer cell lines suppressed tumourigenicity, suggesting it to be a candidate tumour suppressor gene.

Somatic mutations of BRCA1 and BRCA2 have not been found in sporadic ovarian neoplasms, however allelic losses including 17q21, were BRCA1 is located, were common. This suggests that additional tumour suppressor genes are required in the molecular aetiology of sporadic tumours, one proximal to BRCA1, the other on 17p.

Alterations in oncogenes KRAS, MYC and ERBB2 are frequently involved in ovarian carcinogenesis.

KRAS mutations are found in 30% of ovarian carcinomas, and are frequently observed in mucinous adenoma and thus may be an early event in the pathogenesis of ovarian mucinous tumours. KRAS mutations are present in 40-50% of mucinous LMP tumours and mucinous carcinomas, and also in one-third of serous LMP tumours. Amplification of KRAS has been reported in 3-5% of ovarian cancers. In one study, KRAS2 amplification occurred in 2/53 of ovarian epithelial tumours, (6 borderline serous, 2 low grade serous, 31 high grade serous; 4 low grade mucinous; 2 low grade endometrioid, 8 high grade endometrioid), and only in the aggressive types (2 high grade serous tumours). A mutation in codon 12 of KRAS has been identified in small cell carcinoma.

HRAS acquires transforming activity either as a result of substitution mutations or by increased expression of the normal gene. Mutated HRAS lack GTPase activity, resulting in dysregulation of cell growth.

Abnormal cell signalling mediated by protein kinases can result from alterations of the growth factor receptors in ovarian epithelial neoplasms. These include:

Amplification of MYC oncogene, 8q24, occurs in 10-20 % of ovarian cancers, and in about one-third of advanced ovarian carcinomas. MYC amplification is more frequently found in the serous subtypes than the mucinous subtypes. MYC encodes a DNA-binding nuclear-associated protein that regulates cell proliferation. Dividing cells have increased amounts of nuclear c-myc, whereas quiescent cells express negligible quantities. MYC amplification is often indicative of biologically aggressive tumours. MYC amplification was not associated with prognosis or survival. Significantly higher levels of p62c-myc were found in serous papillary ovarian carcinoma. LMP tumours expressed MYC at values intermediate between that of normal ovary tissue and carcinoma.

Amplification, altered expression, and malfunction of several protein kinases and phosphatases are involved in the pathogenesis of ovarian epithelial neoplasms, in particular the phosphatidylinositol 3-kinase (PI3K) pathway. Increased PI3K activity is important in the growth and dissemination of ovarian cancer cells. The PIK3CA gene which encodes the catalytic subunit of PI3K, and its downstream effector AKT2 are amplified in primary ovarian tumours. Overexpression of AKT2 is found in high-grade and late-stage tumours. Mutation and/or down-regulation of the PI3K phosphatase PTEN/MMAC1 are frequently observed in ovarian endometrioid carcinomas. AKT2 mediates some of the transforming signals of RAS and SRC which are mutated and overexpressed/activated respectively in late-stage tumours. Downregulation of the cGMP-dependent protein kinase PKG and upregulation of MAP2K6 (MEK6) were significantly correlated with the genesis of ovarian cancer. Amplification of AKT2 has been reported in 3-5% of ovarian cancers.

Expression Profiling
Amplification of other oncogenes such as FGF3 (formerly INT2) and MDM2 have been reported in 3-5% of ovarian cancers. As mentioned in the Molecular Cytogenetics section, high level amplification of 20q12-q13.2 is a frequent finding in ovarian carcinomas, and a gene located at 20q11.2-12, TGIF2, was amplified and over-expressed in 14 ovarian cancer cell lines. EIF5A2 is a candidate oncogene for the 3q25-q26 amplification in ovarian carcinomas. Overexpression of the Kallikrein gene, KLK4, located at 19q13.4, has been found in 69/147 ovarian tumours and is indicative of a poor prognosis. NME1 is thought to have a role in ovarian neoplastic process. Elevated levels of inhibin are found in most postmenopausal women with mucinous ovarian cancers.

Overexpression of BCL2 is present in about 90% of endometrioid carcinomas, and MSI is present in about one-third of cases, as has been described in endometrioid endometrial carcinomas. Overexpression of P53, EGFR, ERBB2 and ERBB3 was also detected in ovarian endometrioid carcinoma.

Expression microarrays were used to compare differential expression between 7 early stage ovarian carcinomas and 7 late stage ovarian carcinomas, and showed that several genes are aberrantly regulated to the same extent in both groups. Genes which function in cell-cell interaction such as cadherin 11 (CDH11), cadherin 2 (CDH2) and nidogen (NID) were downregulated in most tumours. Genes involved in invasion and metastasis such as matrilysin (MMP7), gelatinase (MMP9), matrix metalloproteinase 10 and 12 were upregulated in most tumours.

Several other expression profiling studies have been undertaken which identified differentially expressed genes between serous and mucinous carcinomas; and also identified differences in gene expression during progression of ovarian carcinoma.