Although breast cancer is common, non-cancerous breast masses are even more common. In these additional articles, fibrocystic change, breast cysts, and fibroadenomas are discussed as frequently encountered non-cancerous breast masses. A breast lipoma is another common non-cancerous breast mass that may be found when performing a self-breast exam.
What is a Lipoma?
A lipoma is a benign (non-cancerous) tumor composed of adipose (fatty) tissue with a thin fibrous capsule around the outside of the mass. Although we are discussing breast lipomas, lipomas can occur anywhere in the soft tissues of the body between the skin and muscle. Lipomas can also occur internally within the body. The most common internal lipoma occurs in the gastrointestinal tract (bowel). These benign fatty tumors can develop at any age but are more frequently encountered after age 40.
When large enough to feel lipomas are soft, pliable, and mobile and will not tether or pull in the overlying skin. Giant lipomas can cause a bulge that is visible on the surface of the breast. There is generally no associated pain related to a lipoma. Although lipomas can slowly enlarge over time, this does not indicate that the mass has become cancerous. Remember lipomas are benign masses that do not turn into cancer.
All new breast lumps should be evaluated by your primary care provider and with diagnostic imaging. Lipomas are not always visible on the mammogram or by ultrasound because the fatty tissue of the mass may blend in with the fatty tissue of the breast or be obscured (masked/covered up) by glandular tissue. When visible on the mammogram a lipoma has a classic appearance which allows the breast radiologist to easily make the diagnosis of lipoma. However, even if the lipoma is visible on the mammogram, a breast ultrasound is usually done to complete the evaluation of a new lump in the breast in order to ensure that no suspicious imaging features are present that may indicate adjacent breast cancer. As with mammography, when visible, lipomas have a very specific imaging appearance on ultrasound which allows the radiologist to make the diagnosis of lipoma.
Lipomas that have the expected imaging appearance on the mammogram and/or breast ultrasound do not need a biopsy for diagnosis. The appearance on imaging is sufficient to make the diagnosis without having to take tissue from the mass to prove it. In fact, a biopsy sample from a lipoma can actually confuse the picture and lead to more invasive procedures. Remember a lipoma is a mass of fatty tissue. One of the two main tissue components of the breast is fatty tissue. After the biopsy, the pathologist will see fatty tissue on the biopsy samples. Because of this the pathologist may question if the targeted mass was adequately sampled which could lead to a surgical biopsy to remove the entire mass to prove that this was, in fact, a non-cancerous lipoma.
Lipomas can be safely left alone once the diagnosis has been made by imaging. It is generally not necessary to have imaging follow-up of the mass or an image-guided biopsy. As with all choices in medicine, the risks of a procedure should be weighed against the potential benefits. In select cases where the lipoma is large enough to distort the contour of the breast, the cosmetic benefit of having the lipoma removed may outweigh the risks of undergoing a surgical procedure. In very rare cases breast lipomas may grow at a faster rate than expected and surgical removal is recommended. But in most cases, the risks related to surgery are far higher than the risk of leaving the lipoma in the breast.
We encourage all women to perform a monthly self-breast exam and to have any new breast changes promptly evaluated by their primary care provider and with diagnostic imaging. If the diagnosis of lipoma is made on diagnostic imaging, rest assured that this is a non-cancerous mass that does not need to be biopsied or surgically removed in the vast majority of cases.