Fat Necrosis and Oil Cysts in the Breast

Fat necrosis happens when an area of the fatty breast tissue is damaged, usually as a result of injury to the breast. It can also happen after breast surgery or radiation treatment. Fat necrosis is more common in older women with very large breasts.

As the body repairs the damaged breast tissue, it’s usually replaced by firm scar tissue. But some fat cells may respond differently to injury. Instead of forming scar tissue, the fat cells die and release their contents. This forms a sac-like collection of greasy fluid called an oil cyst.

Diagnosis

Oil cysts and areas of fat necrosis can form a lump that can be felt, but usually doesn’t hurt. Sometimes the skin around the lump looks thicker, red, or bruised. These changes can be hard to tell apart from cancers on a breast exam or even a mammogram. A biopsy (removing all or part of the lump to look at the tissue under the microscope) may be needed to find out if the lump contains cancer cells.

Oil cysts (like other cysts) can often be seen on ultrasound and then diagnosed by needle aspiration. This is where a thin needle is put into the cyst to take out the fluid.

Treatment

Fat necrosis and oil cysts usually don’t need to be treated. Sometimes fat necrosis goes away on its own.

The needle aspiration done to remove the fluid in an oil cyst can also serve as treatment.

In some cases, surgery may be used to take out the lump or lumpy area if it gets bigger or becomes bothersome.

How do fat necrosis and oil cysts affect your risk for breast cancer?

These breast changes do not increase a woman’s risk of breast cancer.

The American Cancer Society medical and editorial content team
Our team is made up of doctors and master’s-prepared nurses with deep knowledge of cancer care as well as journalists, editors, and translators with extensive experience in medical writing.

Guray M, Sahin AA. Benign breast diseases: Classification, diagnosis, and management. Oncologist. 2006;11;435-449.

Hartmann LC, Sellers TA, Frost MH, et al. Benign breast disease and the risk of breast cancer. N Engl J Med. 2005;353:229-237.

Kerridge WD, Kryvenko ON, Thompson A, Shah BA. Fat necrosis of the breast: A pictorial review of the mammographic, ultrasound, CT, and MRI findings with histopathologic correlation. Radiology Research and Practice. 2015;2015:613139.

National Cancer Institute. Understanding Breast Changes: A Health Guide for Women. April 23, 2015. Accessed at www.cancer.gov/types/breast/understanding-breast-changes on June 1, 2016.

Santen RJ, Mansel R. Benign breast disorders. N Engl J Med. 2005;353:275-285.

Schnitt SJ, Collins LC. Pathology of benign breast disorders. In: Harris JR, Lippman ME, Morrow M, Osborne CK, eds. Diseases of the Breast. 4th ed. Philadelphia, Pa: Lippincott Williams & Wilkins; 2010:69-85.

Last Medical Review: March 16, 2015 Last Revised: April 21, 2016

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