page_title: Necrosis
section_title: Histopathological changes
hierarchical_section_title: Necrosis / Pathogenesis / Histopathological changes
caption_attribution_description: English: Very high magnification (400x) micrograph of a myocardial infarction ("heart attack" in common parlance) showing prominent contraction band necrosis with karolysis (loss of the nuclei), edema and an inflammatory infiltrate consistent of monocytes. Related images High mag.
context_page_description: Necrosis is a form of cell injury which results in the premature death of cells in living tissue by autolysis. Necrosis is caused by factors external to the cell or tissue, such as infection, or trauma which result in the unregulated digestion of cell components. In contrast, apoptosis is a naturally occurring programmed and targeted cause of cellular death. While apoptosis often provides beneficial effects to the organism, necrosis is almost always detrimental and can be fatal.
  Cellular death due to necrosis does not follow the apoptotic signal transduction pathway, but rather various receptors are activated and result in the loss of cell membrane integrity and an uncontrolled release of products of cell death into the extracellular space. This initiates in the surrounding tissue an inflammatory response, which attracts leukocytes and nearby phagocytes which eliminate the dead cells by phagocytosis. However, microbial damaging substances released by leukocytes would create collateral damage to surrounding tissues. This excess collateral damage inhibits the healing process.
context_section_description: The nucleus changes in necrosis and characteristics of this change are determined by the manner in which its DNA breaks down:
  Karyolysis: the chromatin of the nucleus fades due to the loss of the DNA by degradation.
  Karyorrhexis: the shrunken nucleus fragments to complete dispersal.
  Pyknosis: the nucleus shrinks, and the chromatin condenses.
  Other typical cellular changes in necrosis include:
  Cytoplasmic hypereosinophilia on samples with H&E stain. It is seen as a darker stain of the cytoplasm.
  The cell membrane appears discontinuous when viewed with an electron microscope. This discontinuous membrane is caused by cell blebbing and the loss of microvilli.
  On a larger histologic scale, pseudopalisades (false palisades) are hypercellular zones that typically surrounds necrotic tissue. Pseudopalisading necrosis indicates an aggressive tumor.
caption: Karyolysis (and contraction band necrosis) in myocardial infarction (heart attack).
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