Finding a lump in your breast can be scary, but it doesn’t always mean breast cancer. Fat necrosis of the breast occurs when fat and oils collect into a lump that you can feel in your breast tissue. The lump isn’t cancerous, and it typically isn’t painful.

It can be difficult to tell the difference between lumps caused by fat necrosis and lumps caused by breast cancer on a mammogram. In order to make an accurate diagnosis, a doctor may need to take a sample of the tissue with a breast biopsy.

This article explores what causes fat necrosis, who’s at risk, and how these lumps are treated.

Fat necrosis is a noncancerous lump in the breast that develops from dead or damaged breast tissue. When breast tissue is damaged, fat cells in the tissue die and release oils that form small sacs called cysts. Over time, these cysts can harden and lead to the formation of scar tissue.

When you feel a lump from the outside of your breast, it can be difficult to determine the cause. Even on a mammogram, your doctor may not be able to tell the difference between fat necrosis and tumors caused by breast cancer.

Fat necrosis makes up nearly 3 percent of all breast lesions. Sometimes, the only way to tell the difference between these lumps and breast cancer is to do a breast biopsy.

Fat necrosis commonly develops after breast surgery, radiation, or other traumatic injuries to the breast. While the lumps can cause some worry initially, they are harmless in terms of your overall health and don’t increase your risk of developing breast cancer.

Lumps caused by fat necrosis are also rarely painful, but you may have anxiety until breast cancer or other problems are ruled out as the cause of the lump

What to do about a breast lump

Talk with a doctor as soon as you can 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 cancer.

Most of the time, fat necrosis goes away on its own, and any pain or tenderness from the necrosis can be treated.

Fat necrosis causes a firm lump or mass to form in your breast. It’s usually painless, but it can feel tender to some people.

You might also notice some redness or bruising around the lump, but there are rarely any other symptoms.

It can be nearly impossible to tell the difference between a fat necrosis lump and a breast cancer lump by a physical exam or even with a mammogram. If you find a lump in your breast, it’s important you see a doctor right away.

Breast fat necrosis vs. breast cancer symptoms

While it’s difficult to tell the difference between fat necrosis and breast cancer without a biopsy, there are some symptoms that may appear with breast cancer that you would not have with a lump caused by fat necrosis.

Possible signs of breast cancer can include:

  • nipple discharge, which is an early sign
  • 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
  • swollen lymph nodes under your arm or collarbone

It’s not likely that you would experience any of these symptoms with a lump caused by fat necrosis, so it’s best to see a doctor if you notice any of these signs.

Learn about the warning signs of breast cancer.

Breast fat necrosis vs. oil cyst symptoms

Oil cysts can also cause a lump in your breast and sometimes form along with fat necrosis.

Oil cysts are also noncancerous, fluid-filled sacs that form when the oils from decomposing fat cells collect in one place instead of hardening into scar tissue. Your body coats the oil sac with a layer of calcium (calcification), and the sac will feel:

  • smooth
  • squishy
  • flexible

Similar to a lump caused by fat necrosis, a lump is probably the only symptom you’ll notice with an oil cyst. These cysts might show up on mammograms, but they’re usually diagnosed with a breast ultrasound.

Oil cysts usually go away on their own, but your doctor can drain the fluid inside the cyst with a needle aspiration if it’s causing you pain. This will deflate 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:

Typically, women most at risk of breast fat necrosis are of perimenopausal age (around 50 years old) and have pendulous breasts. Pendulous breasts have a longer shape and tend to droop downward more than other breast shapes.

Other demographic factors, such as race, are not associated with a 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.

You might find fat necrosis on your own if you feel a lump, or it might show up on your 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 caused by 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 usually doesn’t need treatment and will go away on its own in time. If you have pain or tenderness around the lump, over-the-counter anti-inflammatory medications like ibuprofen (Advil, Motrin) can help. You can also try massaging the area or applying a warm compress.

Larger lumps that cause more discomfort can be removed surgically, but this isn’t common.

If fat necrosis has led to the formation of an oil cyst, your doctor can drain the fluid with a needle and deflate the cyst.

Fat necrosis can cause a noncancerous lump to form in your breast. These lumps may be uncomfortable or cause concern, but they rarely cause pain or require treatment.

In most cases, these lumps go away on their own and don’t return. A lump caused by fat necrosis doesn’t increase your risk of developing breast cancer or cause any other long-term problems.

Your doctor may need to perform a breast biopsy to make sure your lump is caused by fat necrosis and not breast cancer, so it’s important to talk with a doctor whenever you notice changes in your breast tissue.