Fibroadenomas of the Breast

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

Fibroadenomas are most common in young women in their 20s and 30s, but they can be found in women of any age.

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 borders that are distinct from the surrounding breast tissue. You can move them under the skin and they’re usually firm, but not tender. A woman can have one or many fibroadenomas.


Some fibroadenomas can be felt, but some are only found on an imaging test (like a mammogram). A biopsy (taking out tissue to check it under a microscope) 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.1)


Many doctors recommend removing fibroadenomas, especially if they keep growing or change the shape of the breast.

Sometimes (especially in middle-aged or elderly women) 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 all 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 breast exams regularly to make sure they’re not growing.

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

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.

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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National Cancer Institute. Understanding Breast Changes: A Health Guide for Women. April 23, 2015. Accessed at on June 10, 2016.

1 Complex fibroadenomas. Accessed at on June 10, 2016.

Santen RJ, Mansel R. Benign breast disorders. N Engl J Med. 2005;353:275-285.

Schnitt SJ, Collins LC. Pathology of benign breast disorders. In: Harris JR, Lippman ME, Morrow M, Osborne CK, eds. Diseases of the Breast. 4th ed. Philadelphia, Pa: Lippincott Williams & Wilkins; 2010:69-85.

Last Medical Review: March 16, 2015 Last Revised: April 21, 2016

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