High Yield Image - After an acute MI

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usmle
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#1

This is a high yield USMLE image of a cross section of the heart after an acute myocardial infarction. Diagnose the what is pointed out at the :arrow_down: below:


#2

Coagulative necrosis


#3

Indeed a high yield and it is coagulative necrosis.

What are the other types of necrosis and examples?


#4

coagulative necrosis

  • See this in infarcts in any tissue (except brain)
  • Due to loss of blood
  • Gross: tissue is firm
  • Micro: Cell outlines are preserved (cells look ghostly), and everything looks red

Other types:

Liquefactive

  • 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

  • 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

  • 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

  • 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

  • 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”)

source: http://www.pathologystudent.com/?p=5770