Necrosis

Necrosis (in Greek Νεκρός = Dead) is the name given to unprogrammed death of cells/living tissue (compare with apoptosis – programmed cell death). There are many causes of necrosis including injury, infection, cancer, infarction, inflammation and so on.

There are four distinctive morphologic patterns of necrosis:

Coagulative necrosis – typically seen in hypoxic environments. Cell outlines remain after cell death and can be observed by light microscopy (e.g. myocardial infarction, infarct of the spleen)
Liquefactive necrosis – is associated with cellular destruction and pus formation (e.g. pneumonia)
Caseous necrosis – is a mix of coagulative necrosis and liquefactive necrosis (e.g. tuberculosis)
Fatty necrosis – results from the action of lipases on fatty tissues (e.g. acute pancreatitis)
Fibrinoid necrosis – caused by immune-mediated vascular damage. It is marked by deposition of fibrin-like proteinaceous material in arterial walls, which appears smudgy and acidophilic on light microscopy.

See also