Necrosis
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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.