About Fat Necrosis

Fat Necrosis is a pseudo-mass which may develop within the breast, often presenting as a lump which a woman discovers herself, or it might only show up on a screening mammogram. Fat necrosis almost always occurs as an after-effect of surgery in the breast.

Hector Hector
Does necrosis mean something bad?

Dr. Halls Dr. Halls
In this case, not bad. It happened, then stopped.

The minority of cases come from trauma, like getting punched in the breast. Fat necrosis may also develop following radiation treatments. It is an entirely benign finding. It becomes a cause for concern in breast cancer screening only because its mammographic appearance can mimic breast carcinoma. Because it often presents as a lump, this can cause a woman to worry that it might be breast cancer. But Fat Necrosis is completely harmless and it does not increase risk of future breast cancer development in any way. It is not related to carcinoma at all, but is rather the result of a disruption of oxygen supply to fat cells.

Talking Moose
Talking Moose
What do you mean?

Dr. Halls Dr. Halls
Sometimes, not often, the ‘necrosis‘ word causes too much worry.


For future reference, keep in mind that this page is a wee bit old. Yes, wee wee old! However, there is a new page about fat necrosis.

Fat necrosis occurs when there are large enough accumulations

In the microscopic image below, the darker purple and shriveled bunches are remnants of fat cells that have died. This is ‘fat necrosis‘, and if there are large enough accumulations it can show on a mammogram or possibly grow into a small lump.


What is fat necrosis?

Necrosis‘ means ‘cell destruction‘ or ‘cell death and decay‘. The blood-supply to a fat lobule becomes disrupted, and when the fat cells don’t get enough oxygenated blood, they die. Once a cell dies – any cell in the body and not just the breast, chemical-molecules are released that start the process of trying to get rid of the dead cells. That process includes some enzymes that break-up fat into smaller molecules that can be adsorbed by the bloodstream. The calcium deposits found in fat necrosis are essentially the result of the action of these enzymes.

Are there symptoms of fat necrosis in the breast?

Women with breast fat necrosis may experience fluid discharge from the nipple, and possibly breast pain. Sometimes there is discoloration, or dimpled skin on the surface of the breast. Nipple inversion or retraction is also not uncommon. There may also be no physical symptoms at all.

Breast Cancer Screening mammograms and fat necrosis

Fat necrosis forms into a lump or pseudo-mass due to fat cells that have either died or been damaged, and this will be easily seen on a mammogram X-ray. The only concern is that sometimes the shape and features of a fat necrosis pseudo-mass can be very similar to certain kinds of breast carcinoma. Fat necrosis tends to have an irregular or rounded outline. They tend to be smaller-sized masses, usually less than 2cm in diameter.

Breast X-rays often show a thin outer ring

In the X-ray image of fat necrosis below one can see a thin outer ring shape. That is the outside edge of the fat necrosis build up. Because of the ‘fat density‘ inside the ring, (basically clear, not absorbing light like cancer cells do) one can be quite sure that it is fat necrosis. (Note, however, that most fat necrosis do not have a little round blob in the center like this example does.)


Breast fat necrosis may have a fibrotic reaction

Typically, one observes with fat necrosis quite a bit of liquefied fat and the presence of calcifications. But at other times, depending among on the age of the pseudo-mass, fat necrosis may show more of a ‘fibrotic‘ reaction. This means that fibrous tissue (sometimes called ‘scar tissue‘) has developed in the areas where fat cells have died. In these cases the borders will be thicker, less regular, and possibly speculated. It is these kinds of features, possibly described as an ‘irregular, speculated mass’ which makes screening physicians extra cautious and thorough in ruling out breast cancer.

Radiologists can usually spot fat necrosis lesions

Experienced radiologists can usually recognize subtle features which identify fat necrosis. Often sonograph (ultrasound) images are also taken, as this has proven to be a very useful method of ruling out malignancy. With ultrasound, fat necrosis tends to present with an increased echogenicity of the subcutaneous tissues, and ‘hyperechoic‘ masses are almost always shown to be benign.

Mammograms are still generally the best way to discover fat necrosis

Magnetic Resonance Imaging is sometimes used for additional confirmation of fat necrosis, but its effectiveness is debatable. Even with the greater specificity of MRI, it does not tend to convincingly show those features which would emphatically rule out malignant carcinoma. So, the general consensus seems to be that mammograms are probably the best way to investigate fat necrosis, but where there is any uncertainly at all, a biopsy is initiated.

Treatment of Breast Fat Necrosis

Fat Necrosis requires no treatment. Some family physicians suggest applying warm compresses to the effected breast for about 30 minutes every four hours for a day or so, but generally the situation will just resolve on its own.


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