Borderline Brenner tumour

By Jason Wasserman MD PhD FRCPC
October 5, 2024

A borderline Brenner tumour of the ovary is an uncommon type of ovarian tumour that is more complex than a benign Brenner tumour but does not exhibit the aggressive behaviour of a malignant tumour. It contains cells that are more active and atypical than those in benign Brenner tumours but do not invade surrounding tissues like cancer.

What are the symptoms of this tumour?

Borderline Brenner tumours are often asymptomatic, especially when they are small. However, if the tumour increases in size, it can lead to symptoms similar to other ovarian masses, such as:

  • Abdominal or pelvic pain or discomfort.
  • A feeling of fullness or pressure in the lower abdomen.
  • Abdominal bloating.
  • Unexplained changes in menstrual cycles or abnormal vaginal bleeding (in rare cases).

What causes a borderline Brenner tumour of the ovary?

The exact cause of borderline Brenner tumours is not well understood. They are believed to develop from the surface epithelial cells of the ovary. The process that leads to the borderline features, including more abnormal cell growth and activity than benign tumours, is unclear. Unlike certain ovarian cancers, borderline Brenner tumours do not have a well-defined set of risk factors, such as specific genetic mutations or family history.

How is this diagnosis made?

The diagnosis of a borderline Brenner tumour is typically made after surgical removal and microscopic examination of the tumour by a pathologist. Imaging studies such as ultrasound, CT, or MRI may reveal an ovarian mass, but they cannot definitively distinguish a borderline tumour from a benign or malignant one. Under the microscope, pathologists look for features such as increased cellular activity and atypical cells that do not invade surrounding tissue. Immunohistochemistry (IHC) may also be used to detect specific proteins, confirm the diagnosis, and differentiate it from other types of ovarian tumours.

What does a borderline Brenner tumour look like under the microscope?

When examined under the microscope, borderline Brenner is made up of tumour cells that look very similar to the cells usually found in the bladder. These cells are called transitional cells or urothelial cells. The tumour cells form long finger-like structures that pathologists describe as papillary. Mitotic figures (tumour cells dividing to create new tumour cells) may be found. In a borderline tumour, the cells do not show any evidence of invasion into the connective tissue.

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