Bit · Pathology
Necrosis types — coagulative vs liquefactive vs caseous vs fat vs fibrinoid
Six patterns of cell death after lethal injury. Each has a signature tissue and a signature appearance under the microscope. The pivot is almost always the organ.
Mechanism
Necrosis is unprogrammed cell death after lethal injury (in contrast to apoptosis, which is programmed). The pattern reflects the tissue's structural protein content and the type of injury:
- Coagulative — ischemia in solid organs (heart, kidney, spleen, liver). Cell architecture preserved for days (ghosts), nuclei lost. Protein denaturation dominates.
- Liquefactive — brain ischemia, and bacterial abscesses anywhere. Enzymatic digestion liquefies the tissue. Pus.
- Caseous — TB and systemic fungal infections. Granuloma centre looks like crumbly white cheese. A subtype of coagulative + liquefactive.
- Fat — acute pancreatitis (enzymatic) or breast trauma (non-enzymatic). Free fatty acids bind calcium → chalky saponification.
- Fibrinoid — vessel walls in immune-mediated vasculitis, malignant hypertension, preeclampsia. Pink amorphous fibrin-like material in vessel wall.
- Gangrenous — distal limbs after ischemia. Dry = coagulative under the surface. Wet = superimposed bacterial liquefactive.
Differentiator Table
| Type | Classic setting | Histology / gross | Mechanism |
|---|---|---|---|
| Coagulative | MI, renal infarct, splenic infarct (any solid organ except brain) | Preserved architecture, ghost cells, anuclear | Ischemia → protein denaturation |
| Liquefactive | Brain ischemia, bacterial abscess | Soft, liquefied; pus | Enzymatic digestion (lysosomal / microbial) |
| Caseous | TB, systemic fungi (Histoplasma) | Crumbly white, 'cheese-like' centre of granuloma | Macrophage-walled chronic infection |
| Fat | Acute pancreatitis, breast trauma | Chalky white deposits (saponification with Ca²⁺) | Free fatty acids + calcium |
| Fibrinoid | Vasculitis, malignant HTN, preeclampsia | Pink amorphous fibrin-like material in vessel wall | Immune complexes / plasma protein leak |
| Gangrenous | Distal limbs, GI (mesenteric ischemia) | Dry (coagulative) or wet (+ bacterial) | Ischemia ± infection |
The Pivot
The organ usually gives it away:
- Heart, kidney, spleen, liver after infarct? Coagulative.
- Brain after stroke, or pus anywhere? Liquefactive.
- Granuloma centre, TB, fungal? Caseous.
- Pancreatitis or breast trauma with chalky deposits? Fat.
- Vessel wall in vasculitis or malignant HTN? Fibrinoid.
- Black, dead distal limb? Gangrenous.
NBME-Style Stem
A 64-year-old man with severe substernal chest pain dies 3 days after admission. Autopsy of the left ventricle shows an area where the cellular outlines are preserved but nuclei are absent, with neutrophilic infiltration at the margins. Which type of necrosis is most consistent with these findings?
Concept Anchor
Necrosis pattern follows the tissue: solid organs after ischemia coagulate; brain and pus liquefy; granulomas crumble (caseous); pancreas saponifies (fat); inflamed vessel walls turn pink and amorphous (fibrinoid).