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Types of ovarian cancer

Ovarian cancer is classified into different types on the basis of its histological appearance - that is, how it looks to the pathologist through the microscope. The majority of ovarian cancers fall within the category of epithelial ovarian cancer. The remaining 10% consist of rare types.

Epithelial ovarian cancer

The greatest clinical challenge among gynaecological cancers. Approximately 6900 new cases are diagnosed annually.Three-quarters present with advanced disease, which has spread outside the pelvis.

Within epithelial ovarian cancer (OvCa) there are six subtypes (% frequency in brackets). Each is derived from a different type of tissue in the lower genital tract (also known as the Mullerian tract). However, within invasive cancers there is not a great deal of difference in prognosis for the first three and the distinction is mainly a pathological one.

Serous
 This form accounts for around 70% of cases and is therefore the most common type.

Mucinous
This accounts for a further 10%. These tumours have a slightly worse prognosis than serous tumours.

Endometrioid
These tumours (5%) are more likely to be associated with disease in the uterus (womb) and sometimes an ovary is found to be affected when a woman is diagnosed with endometrial cancer.

Clear cell
These tumours (around 3-4%) have a poorer prognosis and tend to behave more aggressively. Pathologists do not usually grade these tumours since, whether they are Grade I, II or III, this tendency exists and grade is not helpful in predicting prognosis.

Ovacome produces a factsheet that covers clear cell ovarian cancer in more detail; click here to download (pdf).

Borderline tumours
10-15% of ovarian cancers are borderline tumours, also known as tumours of low malignant potential. They tend to remain confined to the ovary for long periods and usually occur in premenopausal women. Implants outside the ovary can arise but there is currently no evidence that the course of this disease is altered by chemotherapy. However, some novel treatments such as matrix metalloproteinase inhibitors may well have a role: the difficulty is establishing a trial in a group of patients with an uncommon disease, as even somebody specialising in the treatment of ovarian cancer will only see a handful of such patients a year.

Treatment of the different types of epithelial cancers is essentially the same. In those fit to receive it the current gold standard is Taxol and a platinum analogue (cisplatin or carboplatin). This is based on the results of two randomised trials conducted in North America and Europe.

Ovacome produces a factsheet that covers clear cell ovarian cancer in more detail; click here to download (pdf).

Germ cell tumours

Germ cell tumours of the ovary make up 3% of malignant ovarian tumours, so they are rare, just one-tenth as common as germ cell tumours of the testis. Hence advances in treatment have largely developed through treatment of the testicular tumours which are of the same origin - from the germ cells of the ovary - in other words the cells that ultimately become eggs.

Germ cell tumours themselves are divided according to their main cell type; they range from embryonal carcinoma at the most undifferentiated end of the spectrum (in other words very immature cells) via immature teratoma through to mature teratoma. The most common type is a dysgerminoma, accounting for 30-40%. A detailed discussion is not realistic within this space but if you have a germ cell tumour of the ovary then you should be managed within a specialist unit with particular experience. They tend to occur in young women (the majority between 10 and 30 years) and adolescents and if managed correctly usually have a good prognosis

The rare forms include:

Ovacome produces a factsheet that covers in more detail the rarer forms of ovarian cancer; please click here to download (pdf).