Fat necrosis of the breast after injury or surgery
Fat necrosis is death (necrosis) of fatty tissue in the breast, usually after an injury or an operation, which leaves a firm lump that can look like cancer.
Remember
After a breast injury or an operation, a new firm lump is more likely to be fat necrosis, a reaction to damaged fat, yet it can still look like cancer and so needs imaging.
Fat necrosis happens when part of the fatty (adipose) tissue of the breast is damaged. Necrosis simply means cell death: the injured fat cells (adipocytes) die.
Usually the damage follows a knock or a seat-belt injury, or a procedure such as surgery or a needle biopsy. Occasionally no cause is found.
The damaged fat triggers inflammation, and the body then repairs it with scar tissue. The scar is felt as a firm, irregular lump, sometimes with skin changes.
On examination and on imaging, the lump can feel and look like breast cancer. Skin tethering (the skin is slightly pulled in over the lump) can make the lump look even more like cancer.
So even when the story fits fat necrosis, a firm lump after breast surgery or injury needs triple assessment: examination, imaging and a needle biopsy (a small tissue sample). Fat necrosis itself is benign, but it can look just like cancer.
A history of breast injury or surgery makes fat necrosis more likely, but assessment is still needed. Steady growth, or fixation to the chest wall, favours a tumour rather than fat necrosis.
Key facts
- Cause
- damage to the fat of the breast, usually after an injury or an operation, though some cases have no clear cause.
- Mechanism
- injured fat cells die, the body responds with inflammation, and the dead fat is then replaced by scar tissue.
- Feel
- a firm, irregular lump, sometimes with changes to the overlying skin.
- On imaging
- calcification (small calcium deposits) can sometimes be seen.
- Pitfall
- it can look and feel like breast cancer on examination and on imaging.
- Action
- ask about previous injury or surgery, and refer for imaging rather than assuming it is benign.
Exam traps
- An abscess (a collection of pus from bacterial infection) gives a hot, red, tender swelling, often with fever, so a firm lump without those features is not explained by infection.
- A rapidly enlarging mass with peau d’orange (dimpled, orange-peel skin) is a worrying sign of an aggressive cancer, whereas fat necrosis is benign and is not rapidly enlarging.
- A soft mobile lump that has stayed unchanged for several years does not support fat necrosis, which usually follows surgery or an injury and feels firmer and more irregular.
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