What is fat necrosis?
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.
Who does fat necrosis affect?
Fat necrosis can affect anyone who sustains an injury to their fatty tissue.
It most commonly affects:
- People with breasts. Fat necrosis most commonly affects breast tissue, and it’s more likely the more breast tissue you have.
- People who’ve had breast surgery, especially involving fat grafting.
- People who’ve undergone radiation therapy for cancer.
- People over the age of 50.
More rarely, it can also affect:
- People who’ve had severe acute pancreatitis.
- Newborns delivered under traumatic conditions.
Where does fat necrosis occur?
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).
Symptoms and Causes
What are the symptoms of fat necrosis?
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.
What does fat necrosis look like?
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.
What does fat necrosis feel like?
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.
Does fat necrosis hurt?
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.
What causes fat necrosis?
Fat necrosis occurs when injury to your adipose tissue causes cells to die. Injuries include:
- Blunt trauma, such as in a car accident.
- Surgical procedures, both therapeutic and cosmetic.
- Biopsy procedures.
- Radiation treatments.
- Injury by pancreatic enzymes in acute pancreatitis.
What are the possible complications of fat necrosis?
- Cosmetic issues. Fat necrosis may cause some procedures, such as breast reconstruction, to fail entirely.
- Re-operation. Fat necrosis resulting from cosmetic surgery may send people back to the operating room to correct it.
- Infection of the tissue. This is a rare but possible complication. It might require antibiotics or surgery.
- Stress. Fat necrosis can be especially stressful for people who are being treated for cancer, who may have come successfully through radiation and surgery only to find themselves returning to the hospital with complications from those treatments. It may mean reoperation or cosmetic deformity, and it may also resemble cancer returning. (It’s not cancerous, but sometimes it’s hard to tell.)
Diagnosis and Tests
How is fat necrosis diagnosed?
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.
What tests are used to diagnose fat necrosis?
Your healthcare provider may suggest different types of imaging tests to identify fat necrosis, including:
- CT scan.
If your healthcare provider needs to confirm fat necrosis in the lab, they might take a needle biopsy.
Management and Treatment
Does fat necrosis go away on its own?
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.
How do you get rid of fat necrosis?
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:
- Fine needle aspiration. This method uses a long, thin needle and syringe to extract cells, tissue and fluids without cutting your skin. The needle can be used to drain an oil cyst, which causes the lump to deflate.
- Vacuum-assisted core needle biopsy. This method uses a wider, hollow needle to extract pieces of tissue through a small incision. Using ultrasound or X-ray imaging to guide the needle, healthcare providers attach a vacuum device to suction tissue through the chamber, similar to liposuction. This method can be done under local anesthesia.
- Excision biopsy. A surgical cut to remove the tissue is a last resort, as surgery can cause further fat necrosis. However, some cases may require excision — for example, if the lump is too big to suck through a needle or if there’s a high suspicion of cancer. This operation may be done under local or general anesthesia. It leaves a small scar.
Outlook / Prognosis
How long does fat necrosis last?
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.
What is the outlook for people with fat necrosis?
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.
When should I be concerned about fat necrosis?
Contact your healthcare provider if your fat necrosis:
- Causes pain.
- Seems to grow.
- Causes new changes after being diagnosed.
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.
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