Fibroadenomas are non-cancerous (benign) lumps of the breast that are characterized by the growth of glandular and connective tissue in the breast. These tumors are more common in the reproductive years. Fibroadenomas rarely occur in women after menopause and commonly regress after menopause. They are the second most common solid tumor after breast cancer and the most common benign tumor in women. Because mammograms are not common in women younger than age 40 these tumors are usually detected through self-examination. (1)

This type of tumor can occur anywhere in the breast tissue. When the woman comes to the physician’s office the tumors usually can be felt as small, full, freely mobile and feel rubbery. They can range in diameter from 1 cm to 15 cm. Interestingly, these types of tumors appear in 50% of the women who received cyclosporine after receiving a renal transplantation. In these cases they are often multiple and in both breasts.

Fibroadenomas can change during the menstrual cycle depending upon hormonal secretions. They can also change during pregnancy but will usually regress and calcify during menopause. During the initial examinations these tumors are usually painless. Women are asked to carefully monitor the size and any changes in feel of the fibroadenomas. (2)

Physicians may request a mammogram as a diagnostic tool or the fibroadenomas may be picked up on mammogram. On the imaging studies fibroadenomas appear round or oval and have a smooth edge to the mass. The outline of the tumor will be clearly defined and can sometimes be accompanied by calcifications. On the mammogram image results it will look more like a cyst or well contained tumor.

If you or your physician suspect that you have a fibroadenoma the doctor or radiologist may request an ultrasound study following the mammogram. This is because the tissue of a fibroadenomas will be easier to distinguish in an ultrasound. It usually appears dark with a definite outline. If there aren’t definitive results with an ultrasound the physician may request a magnetic resonance imaging study, or MRI. However, the most conclusive test is a fine needle biopsy or core needle biopsy to get a sample of the cells for the pathologist to examine. (3)

The exact causes of the fibroadenomas are not known. However, because they commonly regress during menopause and appear most often during the reproductive years or during pregnancy, it is known that they are influenced by estrogen. Inside the breast tissue are 15 to 20 different lobes of glandular tissue that are further divided and produce milk during breast-feeding. Supporting this network of lobes and ducts is a deeper layer of connective tissue. Fibroadenomas are made up of both disconnected tissue and glandular tissue.

Fibroadenomas are benign lesions and researchers have not been able to pinpoint any malignant potential. However, they do contain epithelial cells, which poses a risk of cancer. Researchers have found that the risk of developing a breast cancer with the fibroadenomas is approximately 3%. Approximately 3 to 10% of women in their reproductive years will experience the formation of a fibroadenomas. And of those three to 10% of women, 3% of those may develop breast cancer.

Further statistical analysis has found that cancer is twice as likely to occur in women who previously had a fibroadenomas removed from her breast. However, the relative risk of cancer is increased in women who have fibroadenomas that are also associated with this, calcifications or sclerosing adensosis. Some teenage women find that they develop juvenile fibroadenomas or a giant fibroadenomas, which are rapidly growing tumors and are cured only with excision.

Once the fibroadenomas has been identified it may actually continue to grow and change the exterior shape of the breast. You might consider a surgical removal if leaving the adenoma in place causes anxiety or anyone of the diagnostic tests done to identify the tumor is abnormal. The surgical procedure will be a lobectomy and is often performed under local or general anesthesia. Once a fibroadenomas removed it is possible that new ones can develop and you may need a second surgery to remove them.

Surgery is not required if your physician is reasonably certain that the lump is a fibroadenoma and not breast cancer based on his examination, imaging or biopsy. Surgery at a younger age can distort the shape and texture of the breast and leave scar tissue that will complicate future breast examinations. If you choose not to have surgery it is important to continue monitoring the size, shape and feel of the fibroadenoma and report any changes to your primary care physician or gynecologist. (4)
(1) Fibroadenoma
(2) MedlinePlus: Fibroadenoma
(3) Johns Hopkins Breast Center: Fibroadenoma
(4) Breast Cancer Care: Fibroadenoma


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