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This is the most common type of ovarian tumour and occurs in around nine out of every 10 cases. 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. Find out more about treatment here.

High grade serousWoman drinking tea

High grade serous ovarian cancer (sometimes known as high grade serous carcinoma) is the most common form of epithelial ovarian cancer, accounting for over six of every 10 cases of epithelial cancer. The majority of high-grade serous ovarian cancers are now thought to originate in the fallopian tube, not the ovary. This type of ovarian cancer is usually treated with a combination of chemotherapy and surgery.  

Low grade serous

Low grade serous ovarian cancer (or low grade serous carcinoma) is relatively rare accounting for one of every ten cases of epithelial ovarian cancer. These tumours are often slow growing, and often detected in younger women. Surgery, chemotherapy and hormonal therapy are often used to treat low grade serous ovarian cancer.


Mucinous 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

  • Metastatic from other sites  (spread from somewhere else in the body) which may not be classified primarily as ovarian cancer 

    Ovarian endometrioid

    Ovarian endometrioid tumours may either be endometriosis-associated or non-endometriosis associated and there is gathering evidence these may be quite distinct types. In around a third of ovarian endometrioid tumours there may also be an independent separate endometrial (womb) tumour or endometrial hyperplasia (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 is important to note very many more women have endometriosis than are diagnosed with ovarian cancer. So having endometriosis should not cause undue concern.

    Clear cell


    Natalie's Story

    "When they did the operation they found cysts and a grade III clear cell tumour."

    Clear cell ovarian cancer (also known as clear cell carcinomas) are rare tumours 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. Due to its low rate of incidences 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 is not possible to tell where they have originated. These are usually treated with a combination of surgery and chemotherapy.

    Primary peritoneal

    Primary peritoneal cancer, sometimes referred to as PPC, is similar to epithelial ovarian 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 abdomen - including your bowels, stomach, liver and reproductive organs), which means even women who have had their ovaries removed can develop this type of ovarian cancer. Find out more about primary peritoneal cancer.

    Brenner tumours

    Brenner tumours of the ovary are rare, accounting for one to two per cent of ovarian tumours. The average age at diagnosis is 50 years with over 70 per cent of women diagnosed being over 40 years. Most Brenner tumours are benign (non-cancerous). Less than five per cent are borderline (slow growing) or malignant. Surgery is the most common form of treatment for these tumours.

    Borderline tumours

    Borderline tumours are a separate group of epithelial ovarian tumours, also referred to as 'tumour of low malignant potential' or 'atypical proliferative tumour'. This means they are very slow growing and have not yet begun to spread or damage the tissue around them. They are staged using the same FIGO system as ovarian cancers. They are usually treatable by surgery alone.


    Find out more 


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    Last reviewed: May 2016
    Next review: April 2019