Fat necrosis is death of fat tissue due to injury and loss of blood supply. It can occur from trauma or as a complication of surgery. It can cause hard lumps to form under your skin, resembling tumors. However, it’s harmless and usually goes away on its own.
Necrosis is tissue death, usually involving a loss of blood supply. Fat necrosis occurs in your adipose tissue (fat tissue) when it’s been injured in some way. You may have received blunt trauma to the area or maybe it was damaged in surgery. Fat necrosis is a slow, delayed process with several stages.
As adipose tissue cells begin to die, you may notice changes in the texture or appearance of your skin in the area. You may feel a lump or a hard node under your skin, or the area may appear red, thickened or bruised. This is normal and expected, and usually temporary. Your tissue will eventually repair itself.
Fat necrosis can affect anyone who sustains an injury to their fatty tissue.
It most commonly affects:
More rarely, it can also affect:
It can occur in any area of fatty tissue that’s been injured. It most commonly occurs in breast tissue. Breasts are often the largest and most exposed collection of fatty tissue on your body, so they’re easily impacted by trauma, such as by the seatbelt in a car accident. Breasts are also affected when they’re exposed to cancer treatments and procedures, such as biopsy, radiation therapy and surgery.
Fat necrosis can also occur in other fatty areas such as your abdomen, buttocks and thighs as a result of medical or cosmetic procedures. For example, a tummy tuck may injure your abdominal fat tissue. Fat transfer procedures, such as the Brazilian butt lift (BBL), which take fat from one area and move it to another area, may injure the grafted fat along the way, causing necrosis and failure of the grafted tissue.
A severe case of acute pancreatitis can sometimes cause fat necrosis in the fatty tissue surrounding your pancreas. When corrosive pancreatic enzymes leak into your body, they can inflame and irritate the surrounding tissues. Pancreatic fat necrosis usually affects your abdominal region, but occasionally, it can infiltrate the subcutaneous fat layer under your skin and spread throughout your body (panniculitis).
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You may notice fat necrosis when you see or feel changes in the texture of your fatty tissue and, sometimes, the skin over it. These changes can vary, depending on where and how severe the damage is and how far along in the process you are. You may notice it months or years after the original injury.
You may see a lump or bump under your skin. If much of the fat under your skin has died, it might appear dimpled or to sag. In your breast, fat necrosis might cause your nipple to sink in. When dying fat cells release inflammatory compounds, they can cause your skin to appear red or bruised, or to thicken.
It may feel like a fatty lump or like a hard nodule. A lump occurs in the first stage of fat necrosis. As fat cells die, they release their oily contents, which collect into a pocket called an oil cyst. Over time, the walls of the cyst can calcify, causing them to harden. When cysts begin to break down, they may flatten.
It usually doesn’t, but occasionally, the area may feel a little tender. Subcutaneous fat necrosis associated with panniculitis is more often painful because this type involves chronic inflammation.
Fat necrosis occurs when injury to your adipose tissue causes cells to die. Injuries include:
Fat necrosis can usually be diagnosed with radiology, but there are two possible difficulties.
The first is that fat necrosis often doesn’t appear until long after the injury that caused it. The average time it takes for fat necrosis to produce noticeable changes is about a year and a half after injury. If you don’t remember the injury, or if you didn’t realize your tissue was being injured at the time, you and your healthcare provider may not suspect fat necrosis.
This is where your detailed health history comes in. Your healthcare provider will ask about any prior injuries, procedures and diseases you may have been treated for in the last several years.
The other difficulty is that fat necrosis can resemble cancer, both in physical exams and in imaging tests. Although a history of cancer is a strong indicator of fat necrosis, it can also raise the specter of cancer’s return. You and your healthcare provider will want to know for sure which one it is. In some cases, this might require taking a sample of the tissue to analyze.
Your healthcare provider may suggest different types of imaging tests to identify fat necrosis, including:
If your healthcare provider needs to confirm fat necrosis in the lab, they might take a needle biopsy.
It usually does, over time. If it isn’t causing you pain or stress, there’s no need to treat it or remove it. But if it bothers you or takes too long to go away on its own, you can have it removed.
Healthcare providers use many of the same methods to remove fat necrosis as they would use to take a biopsy. In some cases, a biopsy taken for diagnostic purposes may also serve to remove your fat necrosis. Methods include:
It varies. It may take months to years for fat necrosis to complete its cycle and break down in your body. Sometimes, when different fat cells are at different stages of necrosis, it may seem to be growing or spreading. Over time, though, it should begin to shrink.
Fat necrosis isn’t harmful and usually resolves on its own. It doesn’t lead to harmful complications. If you have it removed, you may end up with a small scar or indentation. If your fat necrosis resulted from a failed fat transfer procedure, you might have to return to surgery to reattempt it or repair it.
Contact your healthcare provider if your fat necrosis:
A note from Cleveland Clinic
Fat necrosis isn’t harmful, but oil cysts under your skin can resemble cancerous tumors. This can make it alarming to discover, especially if you don’t remember being injured or if you’ve had cancer in the past. Medical testing can soon put your fears to rest. But those who may have cancer treatment or reconstructive surgery in their future should be aware of the risk of fat necrosis. If it occurs, even long afterward, you might have to return to the hospital for testing or reoperation.
Last reviewed by a Cleveland Clinic medical professional on 09/12/2022.
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