by Emily Goebel, MD FRCPC
September 5, 2024

A benign Brenner tumour is a rare, non-cancerous (benign) growth that develops in the ovary. Brenner tumours are usually small and do not spread to other body parts. They are often found incidentally during imaging tests or surgery for different conditions.

What are the symptoms of a benign Brenner tumour of the ovary?

Many women with benign Brenner tumours do not experience symptoms, especially if the tumour is small. However, in some cases, symptoms can include:

• Pelvic pain or discomfort: This may occur if the tumour becomes large or presses on nearby structures.
• Abdominal bloating or swelling: A larger tumour may cause a feeling of fullness or bloating in the abdomen.
• Changes in urinary habits: If the tumour presses on the bladder, it can cause more frequent urination.
• Menstrual irregularities: In rare cases, Brenner tumours may cause changes in menstrual cycles, although this is uncommon for benign tumours.

What causes a benign Brenner tumour of the ovary?

The exact cause of benign Brenner tumours is not fully understood. Like many ovarian tumours, they likely result from abnormal cell growth in the ovary. However, benign Brenner tumours are not caused by any known genetic mutations or inherited conditions. These tumours are most commonly found in postmenopausal women, and age may be a factor in their development.

What is the difference between a benign Brenner tumour and a malignant Brenner tumour?

A benign Brenner tumour is a non-cancerous tumour that will not metastasize (spread) to other body parts. In contrast, a malignant Brenner tumour is a type of ovarian cancer made of very abnormal-looking cells that can metastasize to different parts of the body.

How is this diagnosis made?

The diagnosis of a benign Brenner tumour is usually made during a pelvic ultrasound or other imaging studies performed for unrelated reasons. These tumours often appear as solid, well-defined masses on imaging. However, a definitive diagnosis requires examination of the tumour tissue under a microscope, usually done after surgical removal. The pathologist will examine the tissue to determine whether the tumour is benign or malignant (cancerous).

Microscopic features of this tumour

Under the microscope, a benign Brenner tumour has several characteristic features:

• Epithelial nests: These tumours are made up of small nests or clusters of epithelial cells. The cells often resemble transitional epithelium, similar to the cells lining the bladder.
• Fibrous stroma: The epithelial nests are embedded in a dense, fibrous background, which gives the tumour a firm texture.
• Oval-shaped nuclei: The tumour cells typically have oval-shaped nuclei with grooves, sometimes described as resembling “coffee beans.”
• No signs of malignancy: A benign Brenner tumour does not show signs of aggressive or cancerous behaviour, such as invasion into surrounding tissue or increased mitotic activity (cell division).

These microscopic features help pathologists confirm the diagnosis and distinguish benign Brenner tumours from other ovarian tumours.

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