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 starts in the surface layer covering the ovary. There are different types of epithelial ovarian cancer. These include:

• high grade serous
• endometrioid
• clear cell
• low grade serous
• mucinous

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.

High grade serous (including primary peritoneal cancer)

High grade serous is the most common type of epithelial ovarian cancer. It can affect the ovaries, fallopian tubes or the peritoneum. 

Doctors think that most high grade serous cancers start in the cells at the end of the fallopian tube (fimbriae). These early cancer cells then spread to the ovary and grow. So they might sometimes be called fallopian tube cancer or tubo ovarian cancer.

There are different sub types of high grade serous cancer. These include:

• fallopian tube cancer
• primary peritoneal cancer 

Fallopian tube cancer

The fallopian tubes link the ovaries to the womb. Fallopian tube cancer is treated in the same way as high grade serous cancer in the ovary or peritoneum.

Primary peritoneal cancer

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.

Primary peritoneal cancer (PPC) is rare. It mainly affects women. It's very rare in men. Most people are over the age of 60 when they are diagnosed.

PPC is always either stage 3 or stage 4. This is an advanced cancer. It is treated in the same way as high grade serous cancer in the ovary or fallopian tube.

Endometrioid

Endometrioid ovarian cancer is the 2^nd 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 can also 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. 

Low grade serous

Low grade serous ovarian cancers are rare. They are usually diagnosed in younger people and are slow growing. Chemotherapy doesn’t tend to work as well as it does for other types of epithelial ovarian cancer.

Mucinous

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 one of the following:

• non-cancerous (benign) 
• borderline  (contain abnormal cells but are not a cancer)
• cancerous (malignant) 

Chemotherapy doesn’t tend to work as well for mucinous ovarian cancer.

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.

Treatment

Treatment for epithelial ovarian cancer might include:

• surgery
• chemotherapy
• targeted cancer drugs
• hormone treatment
• radiotherapy

The treatment you have depends on several things, including:

• the type of epithelial cancer
• 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