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Traumatic Fat Necrosis:
(Diagram: Traumatic fat necrosis in the breast. Necrotic area is surrounded by lipid filled macrophages and foreign-body giant cells).
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Necrosis This is almost exclusively seen in the female breast especially, if the breast is heavy and pendulous. Essentially it results from the rupture of adipocytes with release of their contents. The released fat undergoes lipolysis and is converted to fatty acids and glycerol. Clinically the lesion appears as a hard lump in the breast, which may give the impression that a malignant neoplasm is present. On slicing the excised specimen one may see a small central cystic area in which some oily droplets are present. At the periphery the adipose tissue is much firmer and also more opaque than usual. Histological examination of conventionally prepared material shows the presence of numerous granular macrophages which contain phagocytosed lipid. Fatty acid crystals are also often present and these excite a foreign body giant cell reaction (multinucleate cells formed as a result of the fusion of macrophages).
Pancreatic Fat Necrosis:
(Diagram: Fat necrosis in acute pancreatitis. The release and activation of lipolytic pancreatic enzymes results in the necrosis of surrounding adipose tissue. The hydrolysis of the triglycerides releases free fatty acids, which precipitate as calcium soaps in the necrotic debris). Another type of fat necrosis is seen in the peritoneal cavity as a consequence of acute hemorrhagic pancreatitis. In pancreatitis the enzymes secreted by the exocrine pancreas are released from the acini and ducts and thus reach the interstitial tissues. The proteolytic and lipolytic enzymes damage the cell membranes and convert the intracellular triglyceride into glycerol and fatty acids. These latter combine with calcium in the interstitial fluid to form soaps which appear as small, intensely white and opaque patches on the adipose tissue of the pancreas, omentum and other areas of the peritoneum.
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