Where do coagulative, caseous, and liquefactive necrosis occur, and can you illustrate them with a diagram?

Anatomical Distribution of Necrosis Types

Coagulative necrosis occurs primarily in solid organs with hypoxic injury (heart, kidney, liver, spleen), caseous necrosis is characteristic of tuberculosis affecting lymph nodes and lungs, and liquefactive necrosis predominates in the brain and bacterial infections.

Coagulative Necrosis

Coagulative necrosis develops when ischemic injury denatures structural proteins while preserving tissue architecture temporarily. This pattern occurs in:

• Myocardial infarction (heart muscle)
• Renal infarcts (kidney)
• Splenic infarcts (spleen)
• Hepatic infarcts (liver, though less common)
• Cerebral infarcts (brain, though this can evolve to liquefactive necrosis) 1

The tissue becomes firm and sharply delimited, with these abnormalities persisting for months or years 1. In cerebral infarcts specifically, coagulative necrosis can show distinctive imaging features including ring-shaped enhancement on CT scans months after onset, reflecting blood flow in small vessels associated with collagen capsule formation 1. Coagulative necrosis in tumors results from chronic ischemic injury due to rapid tumor growth and inadequate vascularization 2.

Caseous Necrosis

Caseous necrosis is pathognomonic for tuberculosis and appears as cheese-like, friable material. Primary locations include:

• Lymph nodes (especially cervical lymph nodes) 3
• Lungs (pulmonary tuberculosis)
• Any site of tuberculous infection

In cervical lymph node tuberculosis, caseous necrosis occurs in 87.88% of cases and frequently coexists with liquefactive necrosis (91.92% of cases) 3. The presence of caseous necrosis significantly increases diagnostic yield when specimens are tested with molecular methods like GeneXpert 3.

Liquefactive Necrosis

Liquefactive necrosis involves enzymatic digestion of dead cells, resulting in liquid viscous mass. This occurs in:

• Brain tissue (any cause of brain injury - infarcts, infections, trauma) 4, 5
• Bacterial abscesses (anywhere in the body)
• Tuberculous lymph nodes (as secondary change) 3
• Post-traumatic compartment syndrome (calcific myonecrosis) 6

In the central nervous system, liquefactive necrosis is the predominant pattern because brain tissue is rich in hydrolytic enzymes and lipids 4, 5. Coxsackie B virus encephalitis demonstrates widespread multifocal areas of liquefaction necrosis, particularly in the cerebrum 4. Acute necrotizing encephalopathy in neonates shows fulminant liquefactive necrosis with extensive hemorrhage diffusely in the cortex 5.

In tuberculous lymphadenitis, liquefactive necrosis samples yield significantly higher diagnostic positivity rates compared to solid-change specimens for all molecular techniques 3.

Clinical Pitfalls

• Brain infarcts can initially show coagulative necrosis but evolve to liquefactive necrosis over days to weeks due to enzymatic digestion
• Tuberculous lesions often show mixed patterns with both caseous and liquefactive necrosis coexisting 3
• Calcific myonecrosis demonstrates both coagulative and liquefactive necrosis with extensive calcification following compartment syndrome 6
• When sampling for diagnostic testing in suspected tuberculosis, prioritize areas of liquefactive necrosis for GeneXpert testing to maximize diagnostic yield 3

Simple Diagram Representation

COAGULATIVE NECROSIS
├─ Heart (MI)
├─ Kidney (infarct)
├─ Liver (infarct)
├─ Spleen (infarct)
└─ Brain (early infarct → evolves to liquefactive)

CASEOUS NECROSIS
├─ Lymph nodes (TB)
└─ Lungs (TB)

LIQUEFACTIVE NECROSIS
├─ Brain (infarcts, infections, trauma)
├─ Bacterial abscesses (any location)
└─ TB lymph nodes (secondary change)