Brenner tumor of the ovary

Brenner tumors are an uncommon and often reassuring type of ovarian growth. The great majority are benign, and even when they are found, they are frequently a surprise — discovered incidentally during imaging or surgery for another reason. Because they make little CA125, the test plays almost no role in finding or tracking them.

What it is and how common it is

Brenner tumors arise from transitional cells — a cell type that resembles the lining of the urinary tract (the bladder and ureters) more than the rest of the ovary. Under the microscope, they form distinctive nests of cells within dense fibrous tissue.

Brenner tumors come in three forms:

• Benign — by far the most common. These are not cancer.
• Borderline (also called atypical proliferative) — an in-between category that is not clearly benign or malignant.
• Malignant — genuinely cancerous Brenner tumors, which are rare.

They are most often found in older women and are usually small and confined to one ovary. Many benign Brenner tumors cause no symptoms at all and are found by chance.

How it behaves on a CA125 test

For Brenner tumors, CA125 is generally unhelpful. Benign Brenner tumors — the vast majority — do not typically raise it, and the test is not used to screen for or monitor them. In the rare malignant Brenner tumor, markers can be variable and are not dependable.

The point here is slightly different from the other subtypes: it is not that a dangerous cancer is hiding behind a normal CA125, but that CA125 simply is not the right tool for this diagnosis. Brenner tumors are identified and characterized by imaging and, ultimately, by pathology — not by a blood marker.

Symptoms and how it’s diagnosed

Most benign Brenner tumors are silent. When symptoms do occur, they tend to reflect the presence of a pelvic mass:

• A feeling of pelvic pressure or fullness
• Pelvic or abdominal discomfort
• Rarely, abnormal bleeding (some Brenner tumors have hormone-related effects)

Because they are often incidental, Brenner tumors are frequently first seen on a transvaginal ultrasound, CT, or MRI performed for another reason. On imaging they can appear as a solid mass, sometimes with areas of calcification. Distinguishing a benign from a borderline or malignant Brenner tumor, however, requires a pathologist to examine the tissue — which is why a suspicious or growing mass is usually removed and examined.

Treatment and outlook

Treatment depends entirely on which type of Brenner tumor is present.

• A benign Brenner tumor is typically managed by surgical removal of the tumor (or the affected ovary), which is generally curative. No chemotherapy is needed.
• A borderline Brenner tumor is also treated primarily with surgery, with follow-up as advised.
• A malignant Brenner tumor is treated like other ovarian cancers, centered on surgery, with chemotherapy considered depending on stage and how completely the tumor is removed. Because malignant Brenner tumors are rare, care is often guided by gynecologic-oncology expertise and, where available, by clinical trial options.

The outlook for benign and borderline Brenner tumors is excellent. For the rare malignant form, prognosis — as with other ovarian cancers — depends on the stage at diagnosis and the success of surgery.

Questions to ask your care team

• Is my Brenner tumor benign, borderline, or malignant?
• Does this mass need to be removed, or can it be monitored?
• If surgery is recommended, how much needs to be removed?
• For a malignant Brenner tumor, is chemotherapy recommended for my stage?
• Should a gynecologic oncologist be involved in my care?

Why this matters to us

Not every ovarian growth is cancer — and knowing the difference brings enormous relief. The Cure Ovarian Cancer Foundation is here for the whole spectrum, from benign findings that need explaining to the rare, aggressive cancers that need better treatments. If this page gave you clarity, please consider supporting our work so we can keep answering questions like yours.

This page is for education and awareness and is not medical advice. Please talk with your own care team about what your specific diagnosis means for you.