| Caseous necrosis | |
|---|---|
 | |
| Micrograph showing caseous necrosis of a tuberculous lymph node. H&E stain. Histological specimens are normally obtained from supraclavicular lymph nodes to demonstrate caseous necrosis. | |
_focus_(6596011395).jpg) | |
| Subpleural caseous necrosis (Ghon focus) | |
| Specialty | Pathology |
| Complications | Lung cavity |
| Causes | Tuberculosis |
Caseous necrosis orcaseous degeneration[1] (/ˈkeɪsiəs/)[2] is a unique form of cell death in which the tissue maintains a cheese-like appearance,[3] appearing as a soft and white proteinaceous dead cell mass. The dead tissue is enclosed within agranuloma, and differs fromcoagulative necrosis in that tissue structure is destroyed. Caseous necrosis is most notably associated withtuberculoma.
The termcaseous means 'pertaining or related tocheese',[4] and comes from the Latin wordcaseus 'cheese'.[2]
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In caseous necrosis no histological architecture is preserved (unlike withcoagulative necrosis).[5][6] On microscopic examination withH&E staining, the area is acellular, characterised by amorphous, roughly granular eosinophilic debris of dead cells,[6] also containing interspersed haematoxyphilic remnants of cell nucleus contents.[5] This caseus necrotic center is enclosed within agranuloma.[6][7]
Caseous necrosis is characteristically associated with tuberculomas.[5][6][7] A similar appearance can be associated withhistoplasmosis,cryptococcosis, andcoccidioidomycosis.[8]
The process begins as infection is recognized by the body andmacrophages begin walling off themicroorganisms orpathogens.[9] As macrophages release chemicals that digest cells the cells begin to die. As the cells die they disintegrate but are not completely digested and the debris of the disintegrated cells clumps together creating soft granular mass that has the appearance of cheese.[9] As cell death begins, the granuloma forms and cell death continues, the inflammatory response is mediated by a type IV hypersensitivity reaction.[10]
Some data suggests that host macrophages associated withgranulomas may prevent effective immune clearance of mycobacteria, due to their epithelioid morphology and associated barrier function.[11]