Coagulative, liquefactive, caseous, fat, fibrinoid and gangrenous
Mnemonic
Six patterns, each with a characteristic tissue:
- Coagulative - the commonest. Architecture preserved, “ghost outlines”. Ischaemia in any solid organ except the brain
- Liquefactive - digestion to a liquid mass. Brain infarction and abscesses
- Caseous - cheese-like, granulomatous. Tuberculosis, fungal infection
- Fat - pancreatitis (enzymatic) and breast trauma. Saponification with calcium
- Fibrinoid - bright pink fibrin-like material in vessel walls. Vasculitis, malignant hypertension
- Gangrenous - a clinical term. Dry is coagulative, wet is with infection and liquefaction
“The brain liquefies, everything else coagulates.” That single exception is the one most often asked, and it is because the brain is rich in lipid and poor in supporting stroma.
Apoptosis is not necrosis: it is energy dependent, affects single cells, causes no inflammation and leaves the membrane intact, whereas necrosis is passive, affects groups of cells and provokes inflammation.
Expansion
| Type | Appearance | Typical cause and site |
|---|---|---|
| Coagulative | Architecture preserved, cells anucleate | Ischaemic infarction in any solid organ except brain |
| Liquefactive | Tissue digested to fluid | Brain infarction, and abscess anywhere |
| Caseous | Cheesy, amorphous, granulomatous | Tuberculosis, some fungi |
| Fat | Chalky white saponification | Acute pancreatitis, breast trauma |
| Fibrinoid | Pink fibrin-like material in vessel walls | Vasculitis, malignant hypertension |
| Gangrenous | Dry (coagulative) or wet (superadded infection) | Limb ischaemia, bowel |
The brain exception is worth understanding: it has little supporting connective tissue and abundant lysosomal enzymes, so infarcted brain liquefies and eventually leaves a fluid filled cavity, whereas infarcted kidney or heart retains its ghost architecture for days.
Fat necrosis in pancreatitis is caused by released lipase digesting fat and the liberated fatty acids binding calcium, which is why it produces hypocalcaemia and calcification.
Distinguish all of these from apoptosis, which is programmed, energy-dependent, affects single cells and provokes no inflammation.