Epithelial ovarian cancer

Epithelial ovarian cancer is the most common type of ovarian cancer. About 90 out of 100 tumours of the ovary (90%) are epithelial.

Epithelial ovarian cancer means the cancer started in the surface layer covering the ovary. There are different types of epithelial ovarian cancer.

Stage and grade system

As well as the type, the grade and stage of your ovarian cancer are very important. They help your specialist to decide what treatment you need.

The stage of a cancer tells you how far it has grown. In epithelial ovarian cancer there are 4 stages, from 1 to 4.

The grade describes how the cells look under a microscope. The less developed the cells look, the higher the grade. Higher grade cancers grow more quickly than low grade.

Types of epithelial ovarian cancer

There are various types of epithelial ovarian cancers:


Serous epithelial ovarian cancer is the most common type. Your doctor examines the cancer under the microscope. They grade your cancer depending on how much the tumour cells look like normal tissue.

The doctor describes it as either;

  • high grade serous ovarian cancer
  • low grade serous ovarian cancer

Doctors now think that most high grade serous ovarian cancers start in cells at the far end of the fallopian tube. Rather than the surface of the ovary. These early cancer cells then spread to the ovary and grow.


Endometrioid ovarian cancer is the 2nd most common type of epithelial ovarian cancer. It can be linked to endometriosis. Most cases of endometrioid ovarian cancer are diagnosed at an early stage and are low grade.  

Some women have endometroid ovarian cancer at the same time as a separate womb (endometrial) cancer.

Clear cell

Clear cell ovarian cancer is rare. It can be linked to endometriosis. The treatment is the same as for high grade serous ovarian cancer. But chemotherapy doesn’t tend to work as well as it does for other types of epithelial ovarian cancer.


Mucinous ovarian cancer is rare. It can be difficult to diagnose. The doctor does tests to check if the cancer started to grow in the ovary. Or if it spread there from somewhere else in your digestive system.

Mucinous tumours can be non-cancerous (benign), borderline or cancerous (malignant).

Undifferentiated or unclassifiable

Some epithelial ovarian cancers are undifferentiated or unclassifiable. These cancers have cells that are very undeveloped. So it is not possible to tell which type of cell the cancer started from.

Cancers very similar to epithelial ovarian cancer

Primary peritoneal cancer and fallopian tube cancer are similar to epithelial ovarian cancer. They are treated in the same way.

Primary peritoneal cancer

Primary peritoneal cancer (PPC) is a rare cancer that starts in the peritoneum. The peritoneum is a layer of thin tissue that lines the inside of the tummy (abdomen). It covers all of the organs within it, such as the bowel and the liver.

Peritoneal cancer is very similar to epithelial ovarian cancer. This is because the lining of the abdomen and the surface of the ovary come from the same tissue when we develop from embryos in the womb.

Fallopian tube cancer

The fallopian tubes link the ovaries to the womb. Fallopian tube cancer is rare. It has similar symptoms and treatment to epithelial ovarian cancer.


Researchers are doing clinical trials. They want to see if rarer types of epithelial ovarian cancer need different treatment to the serous type.

But at the moment, epithelial ovarian cancers are generally treated in the same way.

Treatment includes:

  • surgery
  • chemotherapy
  • targeted cancer drugs
  • radiotherapy

The treatment you have depends on several things, including:

  • the size of your cancer and whether it has spread (the stage)
  • how abnormal the cells look under the microscope (the grade)
  • your general health

Doctors know that some types of epithelial ovarian cancer respond better to chemotherapy than others. The doctor will discuss the advantages and disadvantages of chemotherapy with you. Doctors are less likely to recommend chemotherapy for some types, including:

  • low grade serous ovarian cancer
  • mucinous ovarian cancer that hasn’t spread
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    JA Ledermann and others
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  • Cancer and its management (7th edition)
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    Wiley-Blackwell, 2015

  • Cancer: Principles and practice of oncology (11th edition)
    VT DeVita , TS Lawrence and SA Rosenberg 
    Lippincott, Williams and Wilkins, 2018

  • Epithelial Ovarian Cancer
    Scottish Intercollegiate Guidelines Network (SIGN), November 2013

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  • Ovarian cancer
    GC Jayson and others
    Lancet, 2014. Volume 384, Issue 9951

Last reviewed: 
03 Dec 2021
Next review due: 
03 Dec 2024

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