Fibroadenomas are common benign tumors of the breast. They are made up of an overgrowth of both the glandular and supporting tissues of the breast. Most often found in women between the ages of 15 and 35, fibroadenomas are affected by women’s hormone levels and can grow larger during pregnancy or smaller after menopause.
As many as 10% of women have fibroadenomas. Some women have multiple fibroadenomas, either in the same breast or in the opposite breast. Most often they are found on physical exam as a smooth, firm, painless mass in the breast. They may not be visible on mammogram. Ultrasound is the best radiology test for looking at fibroadenomas. Ultrasound usually shows the very characteristic finding of a smooth mass that is wider than it is tall, but biopsy is the only definitive way to determine if a lesion is a fibroadenoma. Young adolescent women with no abnormal features may be treated with observation only. A core needle biopsy (a biopsy performed with a needle that takes a cylinder of tissue from the lesion) can help distinguish between a fibroadenoma and other types of breast lesions, such as a phyllodes tumor, a rare breast tumor that can look similar to fibroadenomas. Some pathologists describe these lesions as fibroepithelial lesions, which is a broader category that can include both fibroadenomas and phyllodes tumors. If the fibroadenoma has areas of calcification, cysts, or other changes within, it may be described as a complex fibroadenoma.
Not all fibroadenomas need to be removed. There are no strict size criteria for excision of fibroadenomas; however, some studies suggest removal of fibroadenomas that are larger than 2 to 3 cm. Other indications for surgical resection of a fibroadenoma include discomfort, growth on imaging/exam, or uncertain pathologic diagnosis. Fibroadenomas that are not removed can be followed with ultrasound studies every 6 months for 2 years. If they are not increasing in size over this time, further follow-up or treatment is unnecessary. An alternative to surgical removal is cryoablation, which involves the insertion of a probe through a small incision in the skin to freeze the fibroadenoma. Only some women are candidates for cryoablation. In order to be a candidate for cryoablation, the fibroadenoma must have been previously biopsied to confirm the diagnosis; it should also be smaller than 4 cm and must be visible on ultrasound.
Women with simple fibroadenomas and no family history of breast cancer are not at increased risk of breast cancer. Women who have either a family history of breast cancer or a complex fibroadenoma and proliferative disease (“busy breasts” in layman’s terms) have a slightly increased long-term risk of developing breast cancer.
Juvenile fibroadenoma is a special category of fibroadenomas that occur in young girls and teenagers, between age 10 to 18. They can be very large and tend to grow rapidly. It is often recommended that juvenile fibroadenomas be surgically removed.