Fibroadenomas of the Breast

Fibroadenomas are common benign (non-cancerous) breast tumors made up of both glandular tissue and stromal (connective) tissue. 

Fibroadenomas are most common in women in their 20s and 30s, but they can be found in women of any age. They tend to shrink after a woman goes through menopause.

Fibroadenomas can often feel like a marble within the breast. Some fibroadenomas are too small to be felt, but some are several inches across. Fibroadenomas tend to be round and have clear-cut borders. You can move them under the skin and they’re usually firm or rubbery, but not tender. A woman can have one or many fibroadenomas.

Diagnosis

Some fibroadenomas can be felt, but some are only found on an imaging test (like a mammogram or ultrasound). A biopsy (taking out breast tissue to check it in the lab) is needed to know if a tumor is a fibroadenoma or some other problem.

Most fibroadenomas look the same all over when seen under a microscope and are called simple fibroadenomas. But some fibroadenomas have other changes, too, and are called complex fibroadenomas. (Complex fibroadenomas tend to be bigger and tend to occur in older patients.)

How do fibroadenomas affect your risk for breast cancer?

Women with simple fibroadenomas have a slightly increased risk of breast cancer – about 1½ times the risk of women with no breast changes. Complex fibroadenomas seem to increase the risk slightly more than simple fibroadenomas.

Treatment

Many doctors recommend removing fibroadenomas, especially if they keep growing or change the shape of the breast, to make sure that cancer is not causing the changes.

Sometimes these tumors stop growing or even shrink on their own, without any treatment. In this case, as long as the doctors are sure the masses are fibroadenomas and not breast cancer, they may be left in place and watched to be sure they don’t grow. This approach is useful for women with many fibroadenomas that are not growing. In such cases, removing them might mean removing a lot of nearby normal breast tissue, causing scarring that would change the shape and texture of the breast. This could also make future mammograms harder to read.

It’s important for women who have fibroadenomas to have regular breast exams or imaging tests to make sure the fibroadenomas are not growing.

Sometimes one or more new fibroadenomas can grow after one is removed. This means that another fibroadenoma has formed – it does not mean that the old one has come back. 

The American Cancer Society medical and editorial content team
Our team is made up of doctors and master’s-prepared nurses with deep knowledge of cancer care as well as journalists, editors, and translators with extensive experience in medical writing.

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Last Medical Review: September 20, 2017 Last Revised: September 20, 2017

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