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.


Some fibroadenomas are too small to be felt, but some are several inches across. Fibroadenomas can often feel like a marble within the breast. They 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. Some fibroadenomas 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?

Simple fibroadenomas do not seem to increase breast cancer risk by much, if at all. Complex fibroadenomas seem to increase the risk slightly more than simple fibroadenomas.


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. 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 appear 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 oncology certified nurses with deep knowledge of cancer care as well as journalists, editors, and translators with extensive experience in medical writing.

Collins LC, Schnitt SJ. Chapter 9: Pathology of benign breast disorders. In: Harris JR, Lippman ME, Morrow M, Osborne CK, eds. Diseases of the Breast. 5th ed. Philadelphia, Pa: Lippincott Williams & Wilkins; 2014.

Geethamala K, Vani BR, Srinivasa Murthy V, Radha M. Fibroadenoma: A harbor for various histopathological changes. Clin Cancer Investig J. 2015;4:183-187.

Guray M, Sahin AA. Benign breast diseases: Classification, diagnosis, and management. Oncologist. 2006;11;435-449.

Hartmann LC, Sellers TA, Frost MH, et al. Benign breast disease and the risk of breast cancer. N Engl J Med. 2005;353:229-237.

Nassar A, Visscher DW, Degnim AC, et al. Complex fibroadenoma and breast cancer risk: A Mayo Clinic Benign Breast Disease Cohort Study. Breast Cancer Res Treat. 2015;153:397-405.

Orr B, Kelley JL. Benign breast diseases: Evaluation and management. Clin Obstet Gynecol. 2016;59(4):710-726.

Sabel MS. Overview of benign breast disease. UpToDate. 2019. Accessed at on August 11, 2019.

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

Last Medical Review: September 10, 2019 Last Revised: September 10, 2019

American Cancer Society medical information is copyrighted material. For reprint requests, please see our Content Usage Policy.