Canadian Cancer Society logo

Ovarian cancer

You are here: 

Tumours of borderline malignancy

Tumours of borderline malignancy are epithelial tumours that don’t clearly appear to be cancerous. They account for approximately 15% of all epithelial ovarian tumours. They may occur in one or both ovaries.

These tumours are also known as:

  • tumours or ovarian cancer of low malignant potential (LMP)
  • borderline tumours
  • atypical proliferative tumours
  • borderline epithelial ovarian cancer

Tumours of borderline malignancy are different from typical ovarian cancers.

  • Although the cells of the tumour appear malignant (cancerous), they have not invaded the underlying or nearby tissue.
  • If they spread outside the ovary into the abdominal cavity, they may grow on the lining of the abdomen, but they don’t grow into it.
  • The tumours grow slowly and most are stage I at diagnosis.
  • The tumours tend to develop in women at a younger age than most ovarian cancers.

Types of tumours include:

  • serous tumours
  • mucinous tumours (gastrointestinal type or endocervical-like type)
  • endometrioid tumours
  • clear cell tumours
  • transitional cell tumours (Brenner tumour) – usually benign


Parker Murchison My favourite thing about Camp Goodtime is being able to hang out with other kids who have survived cancer. They know what is going on in your life and can help you get through it.

Read Parker's story

Clinical trial discovery improves quality of life

Illustration of test tubes

A clinical trial led by the Society’s NCIC Clinical Trials group found that men with prostate cancer who are treated with intermittent courses of hormone therapy live as long as those receiving continuous therapy.

Learn more