Necrosis:

“Necrosis refers to a spectrum of morphologic changes

that follow cell death in living tissue, largely resulting

from progressive degradative action of enzymes on the

lethally injured cells”.

Necrosis Apoptosis

1. Cell size: enlarged.

2. Nucleus: Pyknosis-Karyorrhexis- Karyolysis.

3. Plasma membrane: disrupted

4. Cellular contents: leak out, enzymatic digestion.

5. Inflammation +++

6. Role: always pathologic.

7. Agarose gel electrophoresis: diffuse smearing pattern

1. Reduced.

2. Fragmentation.

3. Intact; altered structure.

4. Intact; released into apoptotic bodies.

5. No.

6. Physiologic/ pathologic.

7. Ladder pattern

Why Inflammation around it???

Necrotic cells are unable to maintain the membrane

integrity and their contents often leak out.

This will elicit inflammation in the surrounding tissue.

Morphology:

Increased Eosinophilia: attributable to loss of normal

basophilia imparted by RNA in the cytoplasm.

More glassy homogeneous appearance.

Cytoplasmic vacuolation: due to digestion of cytoplasmic

organelles –moth eaten appearance.

Nuclear changes: 3 forms--

1. Pyknosis: Nuclear shrinkage and increased basophilia---

DNA is condensed to solid, basophilic mass.

2. Karyorrhexis: Fragmentation of the pyknotic nucleus.

3. Karyolysis: Basophilia of the chromatin may fade—DNAase

activity++

Morphology: ……

Dead cells –replaced by:

Large, whorled phospholipid masses called Myelin figures

Calcification

Phospholipids are degraded into fatty acids which undergo

calcification to yield Calcium soaps.

Morphology: ……

Electron microscopy:

Discontinuous plasma membrane

Dilatation of mitochondria with appearance of Large

amorphous densities

Amorphous osmiophilic debris

Aggregates of fluffy material—denatured protein.

1. Coagulative Necrosis

2. Liquefactive Necrosis

3. Caseous Necrosis

4. Enzymatic Fat Necrosis

1. Coagulative Necrosis:

Implies preservation of basic outline of the coagulated cell

at least for some days.

Example: Myocardial infarction—acidophilic, coagulated,

anucleate cells persisting for few weeks.

Ultimately it is removed by phagocytosis by scavenger

leukocytes.

2. Liquefactive Necrosis:

MC hypoxic death in CNS.

Transformation of tissue into a liquid viscous mass.

Seen in fungal/ bacterial infections also.

Pus: creamy yellow material containing dead white

cells.

3. Caseous Necrosis:

Most often seen in TUBERCULOSIS.

Cheesy white- gross appearance of the area of necrosis.

Amorphous, granular debris enclosed within a distinctive

inflammatory border known as Granulomatous

inflammation.

4. Fat Necrosis:

Due to release of activated pancreatic lipases—into

pancreatic substances and peritoneal cavity–destroying the

fat.

MC seen in acute pancreatits.

Lipases split triglycerides into fatty acids that combine with

calcium to produce grossly visible chalky white areas- FAT

SAPONIFICATION.