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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 can be up to several inches across. A woman can have one or many fibroadenomas.
Fibroadenomas can often feel like a marble within the breast. They tend to be round or oval and have clear-cut borders. You can move them under the skin, and they’re usually firm or rubbery, but not tender. Some fibroadenomas are only found by an imaging test (such as a mammogram or ultrasound).
A breast biopsy (removing some breast tissue to check it in the lab) may be needed to know for sure if a breast mass is a fibroadenoma (or some other condition).
Most fibroadenomas look the same all over when seen under a microscope. These 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.)
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.
Most fibroadenomas don't need to be treated. But doctors might recommend removing them in some cases, especially if they keep growing or change the shape of the breast.
Sometimes fibroadenomas stop growing or even shrink on their own, without any treatment. As long as the doctor feels sure the masses are fibroadenomas and not breast cancer, they can often be left in place and watched to be sure they don’t grow. This approach is useful for women with many fibroadenomas that aren't growing. In such cases, removing them might mean removing a lot of nearby normal breast tissue, causing scarring and changes in the shape and texture of the breast.
It’s important that women with fibroadenomas 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 usually 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.
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Last Revised: January 25, 2022
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