Necrosis and types of Necrosis , General pathology
Coagulative
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See this in infarcts in any tissue (except brain)
Due to loss of
... [Show More] blood
Gross: tissue is firm
Micro: Cell outlines are preserved (cells look ghostly), and everything looks red
Liquefactive
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See this in infections and, for some unknown reason, in brain infarcts
Due to lots of neutrophils around releasing their toxic contents, “liquefying” the tissue
Gross: tissue is liquidy and creamy yellow (pus)
Micro: lots of neutrophils and cell debris
Caseous
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See this in tuberculosis
Due to the body trying to wall off and kill the bug with macrophages
Gross: White, soft, cheesy-looking (“caseous”) material
Micro: fragmented cells and debris surrounded by a collar of lymphocytes and macrophages (granuloma)
Fat necrosis
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See this in acute pancreatitis
Damaged cells release lipases, which split the triglyceride esters within fat cells
Gross: chalky, white areas from the combination of the newly-formed free fatty acids with calcium (saponification)
Micro: shadowy outlines of dead fat cells (see image above); sometimes there is a bluish cast from the calcium deposits, which are basophilic
Fibrinoid necrosis
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See this in immune reactions in vessels
Immune complexes (antigen-antibody complexes) and fibrin are deposited in vessel walls
Gross: changes too small to see grossly
Micro: vessel walls are thickened and pinkish-red (called “fibrinoid” because the deposits look like fibrin deposits)
Gangrenous necrosis
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See this when an entire limb loses blood supply and dies (usually the lower leg)
This isn’t really a different kind of necrosis, but people use the term clinically so it’s worth knowing about
Gross: skin looks black and dead; underlying tissue is in varying stages of decomposition
Micro: initially there is coagulative necrosis from the loss of blood supply (this stage is called “dry gangrene”); if bacterial infection is superimposed, there is liquefactive necrosis (this stage is called “wet gangrene”) [Show Less]