Non-Cancerous Breast Conditions

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Fat necrosis and oil cysts

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 surgery or radiation treatment. It’s more common in women with very large breasts.

As the body repairs the damaged tissue, it’s 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.


Oil cysts and areas of fat necrosis can form a lump that can be felt. These can be hard to tell apart from cancers by 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 learn if cancer is present.

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


Fat necrosis and oil cysts usually don’t need to be treated. And 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 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.

Last Medical Review: 03/16/2015
Last Revised: 04/21/2016