What Are Benign Breast Oil Cysts?

self-breast exam. Ian Hootan, Getty Images

Question: What Are Breast Oil Cysts?

After breast surgery or injury, small flexible lumps may appear. They feel squishy, smooth, and similar to a water balloon. Could these be simple cysts or oil cysts? What should you do?


Breast oil cysts are benign breast lumps that usually don't require treatment. Similar to simple cysts, oil cysts are fluid-filled sacs that may feel smooth and squishy. If you've recently had breast cancer surgery, the last thing you want to find is a new lump in your breast.

Don't panic -- but get any breast lump checked out. Let's take a look at oil cysts, and how you can deal with them.

Also Known As: oil cyst, mammary oil cyst, oil cyst of breast

Similar To: lipoma (fatty lump under the skin), hematoma, seroma

How An Oil Cyst Forms

Breast oil cysts may occur after breast surgery, breast reconstruction, an injury to your breast, or they may grow spontaneously. They are called oil cysts because they contain a liquid form of body fat. If you have a lumpectomy or mastectomy, fat tissue may die as your body is healing and attempting to form a scar. Fat necrosis can form into hard scar tissue, or it can melt. The melted fat collects in one area and your body causes a thin layer of calcium to form around it. This eggshell calcification gives your doctor a clear idea of your diagnosis. Simple and complex cysts do not have the calcium layer, but oil cysts are usually enclosed partially or totally by calcium.

Best Way To Diagnose Breast Oil Cysts

An oil cyst can show up on a mammogram, but an ultrasound will give you a clearer picture. A breast ultrasound will use sound waves bouncing off breast tissues to create an image of masses, lumps, and cysts. Because cysts are filled with fluid, gas, or semisolid substances, they appear on ultrasound as dark, smooth-edged circular or oval areas.

These cysts have a clear outline that distinguishes them from surrounding tissues. Other types of breast lumps will appear on ultrasound with different characteristics. Oil cysts will also show up on a breast MRI.

Dealing With An Oil Cyst

Oil cysts are benign lumps -- they are not cancerous and they don't cause breast cancer. If you are diagnosed with an oil cyst, you have some options for dealing with it. An oil cyst may be left alone, as many of these will shrink on its own. But in case your oil cyst becomes physically painful or causes you worry or distress, it can be aspirated. Your doctor can use a very fine needle to suction the fluid out of the cyst, which will deflate it. Aspirated fluid from an oil cyst will be evaluated if it looks bloody. If the cyst is large or has a coarse calcium layer, your doctor might recommend surgical removal.


For Women Facing a Breast Biopsy. Other benign breast conditions: Fat Necrosis. American Cancer Society. Updated 04/20/2009.

Fat necrosis of the breast: clinical, mammographic and sonographic features. Isil Günhan Bilgen, Esin Emin Ustun, Aysenur Memis. European Journal of Radiology - August 2001 (Vol. 39, Issue 2, Pages 92-99).

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