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Fat Necrosis and Oil Cysts in the Breast
Fat necrosis is a benign (noncancerous) breast condition that can develop when an area of fatty breast tissue is injured. It can also develop after breast surgery or radiation treatment.
Stages of fat necrosis
There are different stages of fat necrosis:
- As fat cells die, they release their contents. This forms a sac-like collection of liquid called an oil cyst.
- Over time, small deposits of calcium called calcifications can form around the walls of the cyst. These can often be seen on mammograms.
- As the body repairs the damaged breast tissue, it's usually replaced by more dense scar tissue.
Diagnosis of fat necrosis and oil cysts
Oil cysts and areas of fat necrosis can form a lump that might be felt, but it usually doesn’t hurt. The skin around the lump might look thicker, red, or bruised.
Sometimes these changes can be hard to tell apart from cancer on a breast exam or even a mammogram.
Doctors can usually tell an oil cyst by the way it looks on a mammogram or breast ultrasound. But if it could be something else, a fine needle aspiration or core needle biopsy might be done.
How do fat necrosis and oil cysts affect breast cancer risk?
These breast changes do not affect your risk of breast cancer.
Do fat necrosis and oil cysts need to be treated?
As long as doctors are sure of the diagnosis, fat necrosis and oil cysts usually don’t need to be treated. Sometimes fat necrosis goes away on its own. A needle biopsy to remove the fluid in an oil cyst can also be a form of treatment.
However, if the lump gets bigger or becomes bothersome, surgery may be done to remove it.
- Written by
- References
Developed by the American Cancer Society medical and editorial content team with medical review and contribution by the American Society of Clinical Oncology (ASCO).
Collins LC, Schnitt SJ. Chapter 9: Pathology of benign breast disorders. In: Harris JR, Lippman ME, Morrow M, Osborne CK, eds. Diseases of the Breast. 5th ed. Philadelphia, Pa: Lippincott Williams & Wilkins; 2014.
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. Radiol Res Pract. 2015;2015:613139.
Sabel MS. Overview of benign breast diseases. UpToDate. 2026. Accessed at https://www.uptodate.com/contents/overview-of-benign-breast-diseases on March 13, 2026.
Last Revised: May 26, 2026
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