If you feel a lump in your breast, it may be fat necrosis. Fat necrosis is a lump of dead or damaged breast tissue that sometimes appears after breast surgery, radiation, or another trauma. Fat necrosis is harmless and doesn’t increase your cancer risk. It usually isn’t painful, but it can cause anxiety.

You should tell your doctor about any lumps you feel in your breast. They can do an exam and run any necessary tests to tell you if the lump is fat necrosis or cancerous. Most fat necrosis goes away on its own, but pain from the necrosis can be treated.

Fat necrosis causes a firm lump or mass in your breast. It’s usually painless, but it can be tender in some people. You might also have some redness or bruising around the lump, but there are usually no other symptoms. A fat necrosis lump feels the same as a breast cancer lump, so if you find a lump in your breast, see your doctor.

There are some signs of breast cancer in addition to a lump. Other early signs of breast cancer can include:

  • nipple discharge
  • changes to your nipple, such as turning inward
  • scaling or thickening of the skin on your breast, which is also known as peau d’orange

You are unlikely to experience these additional symptoms from fat necrosis.

Read more: Warning signs of breast cancer »

Oil cysts can also cause a lump in your breast. Oil cysts are benign, or noncancerous, fluid-filled sacs that can appear in your breast. Like other cysts, they will most likely feel smooth, squishy, and flexible. Oil cysts can form for no reason, but they often appear after breast surgery or trauma. As your breast heals from surgery or trauma, breast fat necrosis can “melt” instead of hardening into scar tissue. The melted fat can collect in one place in your breast and your body will cause a layer of calcium to form around it. This melted fat surrounded by calcium is an oil cyst.

If you have any oil cyst, the lump is probably the only symptom you’ll notice. These cysts can show up on mammograms, but they’re usually diagnosed with a breast ultrasound.

In many cases, an oil cyst will go away on its own, so your doctor might recommend “watchful waiting.” If the cyst is painful or is causing you anxiety, a doctor can use needle aspiration to drain the fluid. This usually deflates the cyst.

Necrosis means cell death, which happens when cells do not get enough oxygen. When fatty breast tissue gets damaged, a lump of dead or damaged tissue can form. Fatty breast tissue is the outer layer of the breast beneath the skin.

Fat necrosis is a side effect of breast surgery, radiation, or other trauma such as an injury to the breast. The most common cause is surgery, including:

Older women with large breasts are at increased risk for fat necrosis. Other demographic factors, such as race, are not associated with higher risk of fat necrosis.

Fat necrosis is most common after breast surgery or radiation, so having breast cancer will raise your risk of fat necrosis. Breast reconstruction after cancer surgery may also increase your risk of fat necrosis. For example, there is some evidence that using large “flaps” or filling tissue expanders with large volumes during breast reconstruction can lead to increased risk of fat necrosis.

You might find fat necrosis on your own if you feel a lump, or it might show up on a regular mammogram. If you find a lump yourself, your doctor will do a breast exam, and then a mammogram or ultrasound to determine if the lump is fat necrosis or a tumor. They might also do a needle biopsy to see if there are cancer cells in the lump.

If your doctor finds the lump on a mammogram, they might follow up with an ultrasound or biopsy. Usually, more than one test is necessary to make a definitive diagnosis of fat necrosis.

Fat necrosis doesn’t usually need to be treated, and it often goes away on its own. If you have any pain, you can take ibuprofen (Advil, Motrin) or apply a warm compress to the area. You can also gently massage the area.

If the lump becomes very big or bothers you, a doctor can do surgery to remove it. However, surgery is rarely used for the treatment of fat necrosis.

If there’s an oil cyst in the necrosis, your doctor can use needle aspiration to treat the cyst.

Fat necrosis usually goes away on its own in most people. If it doesn’t go away, you can have surgery to remove it. Once fat necrosis goes away or is removed, it’s unlikely to come back. Having fat necrosis doesn’t increase your risk of breast cancer.

While fat necrosis is benign and usually harmless, it’s important to be aware of any changes in your breast. Contact your doctor if you feel another lump, your necrosis doesn’t go away on its own, or you begin having a lot of pain.