This page was reviewed under our medical and editorial policy by
Anita Johnson, MD, FACS, Chief of Surgery, Atlanta; Leader, Atlanta Women's Cancer Center.
This page was reviewed on February 7, 2022.
A fibroadenoma is a solid, not liquid-filled, lump found in the breast. They are among the many causes of breast changes and often shrink after menopause.
Breasts contain what are called stromal and epithelial connective tissue cells. These cells have receptors for the hormones, estrogen and progesterone. Fibroadenomas are formed from those two types of tissues.
In most cases, these lumps are simple, benign breast tumors that don’t lead to cancer or increase a woman’s risk for breast cancer.
If you have a fibroadenoma, it may feel like a marble under the surface of the skin. They usually are found in the upper, outer quadrant of the breast and have these features:
It’s important to note that they may vary in size. Some are so small, they are only detected during imaging, such as during a mammogram or on an ultrasound. Others are quite large, spanning several inches across the breast.
About 10 percent of women have a fibroadenoma at least once in her lifetime. Fibroadenomas typically show up in your 20s or 30s, but they may be found at any age. For women under 30, fibroadenomas are the most common benign breast tumor. They may also be found in children ages 10 to 18 years. When that happens, they are called juvenile fibroadenomas.
What causes fibroadenomas to form isn’t certain, but it’s possible that the female reproductive hormone estrogen plays a role. These lumps do seem to be influenced by hormones: They’re known to grow during pregnancy and shrink during menopause. They may also grow during puberty. Women who take oral contraceptives at a young age—before 20—have higher rates of fibroadenomas. Sensitivity to the hormones may cause an excessive proliferation of the connective tissues.
A large cohort study of more than 58,000 women in JNCI Cancer Spectrum showed that several risk factors for fibroadenomas are similar to those for breast cancer, like education level and family history of breast cancer. Similar factors that appear to reduce the risk of breast cancer were also protective for fibroadenomas in the study, such as older age at first period, having more children and larger childhood body size. Further research is needed to validate these findings and identify which women are at highest risk of developing breast cancer after fibroadenoma, which is rare.
Diagnosing a fibroadenoma starts with a review of your medical history and an exam. Certain factors may help lead to a diagnosis, including:
The next steps may include:
A mammogram or breast ultrasound may be used to help identify the mass.
A mammogram is a type of X-ray in which images are taken while your breast is pressed between plastic plates. It’s more often used in women over 35 and is read by a radiologist. It may be used for screening or diagnosis. The fibroadenoma appears on these X-rays with smooth, round edges.
An ultrasound is used for women younger than 35. It shows fibroadenomas as round or oval masses. The ultrasound uses sound waves—hence the name—to show whether a mass is solid or filled with fluid.
A core needle biopsy involves removing breast tissue in a way that’s minimally invasive. The samples are about the size of a piece of rice. You may expect some bruising, but usually not scarring.
A pathologist then examines the tissue under a microscope in a lab.
It’s often necessary to perform a biopsy to identify the lump as a fibroadenoma or something else, especially in women in their 20s and older.
Fibroadenomas may be hard to differentiate on an ultrasound or mammogram from a connective tissue tumor known as a phyllodes tumor. Those tumors are rare overall, but they’re most often experienced by women in their 40s. The two types of lumps may be better differentiated with a core needle biopsy.
Fibroadenomas often go away on their own. Those that have not been removed typically shrink after menopause.
Your doctor may recommend removing them or monitoring them, depending on the circumstances.
Sometimes monitoring makes the most sense in these cases:
Still, many doctors do recommend removing a fibroadenoma, especially if:
Removal may involve these options:
Surgery: This is often recommended if the fibroadenoma is growing rapidly or is greater than 2 cm in size. It may also be the right choice if you, the patient, want the fibroadenoma removed. It may be removed by a surgical procedure called a lumpectomy, then sent to a lab to be evaluated.
Cryoablation: This treatment freezes the fibroadenoma using a cryoprobe, which destroys the cellular structure of the fibroadenoma. A core needle biopsy must be performed before cryoablation to confirm that it is, in fact, a fibroadenoma.
Radiofrequency ablation: This process uses high-frequency energy to destroy the fibroadenoma using an ultrasound to focus the energy beam without destroying nearby tissues.
You’ll likely go home the same day after one of these procedures.
It’s possible for one or more new fibroadenomas to appear after one is removed. This is not the return of the previous fibroadenoma—it’s a new one.