Find out about the most common type of ovarian tumour that occurs in around nine out of every ten cases of ovarian cancer.
These tumours arise from the cells that line or cover the ovaries and fallopian tubes (the epithelium).
There are several different subtypes of epithelial ovarian cancer, which can behave and respond differently to treatment.
Sometimes known as high-grade serous carcinoma, this is the most common form of epithelial ovarian cancer, accounting for over six of every ten cases of epithelial ovarian cancer.
The majority of high-grade serous ovarian cancers are now thought to originate in the fallopian tube, not the ovary, and may therefore be classified as fallopian tube cancers. This type of ovarian cancer is usually treated with a combination of chemotherapy and surgery.
Sometimes known as low-grade serous carcinoma, this is a relatively rare form of epithelial ovarian cancer, accounting for one of every ten cases of epithelial ovarian cancer. These tumours are often slow growing, and often detected in younger women.
Surgery is the most effective treatment for low-grade serous ovarian cancer, although chemotherapy and hormonal therapy are also used.
These tumours make up a small percentage of epithelial ovarian cancers. This type of ovarian cancer is usually treated with surgery with or without chemotherapy.
Mucinous tumours are categorised as:
primary ovarian carcinomas (tumours originating in the ovary)
metastatic from other sites (spread from somewhere else in the body, most often from bowels or stomach), which may not be classified primarily as ovarian cancer.
Women with mucinous cancer cells in the ovary therefore often require other tests like colonoscopy or gastroscopy (a small camera inserted into the back passage or into the stomach) to exclude another primary cancer.
Ovarian endometrioid cancers may either be endometriosis-associated or non-endometriosis-associated, and there's growing evidence these may be quite distinct types.
In around a third of ovarian endometrioid cancers there may also be an independent separate endometrial (womb) cancer or endometrial hyperplasia (precancerous thickening of the lining of the womb). This type of ovarian cancer is usually treated with a combination of chemotherapy and surgery, and additionally hormonal therapies such as Letrozole or Anastrozole (aromatase inhibitors – drugs that block oestrogen from being made), can be used.
It's important to note that many more women have endometriosis than are diagnosed with ovarian cancer, so having endometriosis should not cause undue concern.
Also known as clear-cell carcinoma, this is a rare tumour type accounting for four per cent of ovarian tumours.
Ovarian clear-cell carcinomas are still treated in the same way as other epithelial ovarian cancers with a combination of surgery and chemotherapy, but are a more aggressive type of cancer than serous ovarian cancer. As clear-cell ovarian cancer is not very common there have been few trials specifically looking at the best treatments for ovarian clear-cell carcinomas.
Undifferentiated or unclassified
Many epithelial ovarian cancers are termed unclassified or undifferentiated. This is because they have cells that are very underdeveloped, and it's not possible to tell where they have originated. These are usually treated with a combination of surgery and chemotherapy.
These tumours are rare, accounting for one to two per cent of ovarian tumours. They most commonly affect women over 40 years of age.
Most Brenner tumours are benign (non-cancerous) and fewer than five per cent are borderline (slow growing) or malignant. Surgery is the most common form of treatment for these tumours.
Borderline tumours are a separate group of epithelial ovarian tumours, also referred to as 'tumours of low malignant potential'. This means they are very slow growing and less likely to spread around the organs in the abdomen (tummy). Even when they spread they do not damage the tissues around them.
They are staged using the same FIGO/TNM system as ovarian cancers. They are usually treated by surgery alone.
These are high-grade epithelial tumours that contain tissue that looks like both an epithelial cancer and a connective tissue cancer (a sarcoma). They actually behave like high-grade epithelial cancers and are treated in the same way with chemotherapy and surgery.
A note on primary peritoneal cancer
Primary peritoneal cancer, sometimes referred to as PPC, is similar to epithelial ovarian or fallopian tube cancer and is usually classed and treated in the same way. However, it does not originate in the ovaries but in the lining of the peritoneum (a large, thin, flexible sheet of transparent tissue that covers the organs inside your tummy/abdomen – including your bowels, stomach, liver and reproductive organs). This means even women who have had their ovaries removed can develop this type of ovarian cancer.