Tuberculous lymph node with caseating granuloma 40X

Caseous necrosis or caseous degeneration () is a unique form of cell death in which the tissue maintains a cheese-like appearance.Robbins and Cotran: Pathologic Basis of Disease, 8th Ed. 2010. Pg. 16 It is also a distinctive form of coagulative necrosis. The dead tissue appears as a soft and white proteinaceous dead cell mass.

Etymology

The word ''caseous'' means 'pertaining or related to

cheese Cheese is a dairy product produced in wide ranges of flavors, textures, and forms by coagulation of the milk protein casein. It comprises proteins and fat from milk, usually the milk of cows, buffalo, goats, or sheep. During product ...

', and comes from the Latin word ''caseus'' 'cheese'.

Necrosis Necrosis () is a form of cell injury which results in the premature death of cells in living tissue by autolysis. Necrosis is caused by factors external to the cell or tissue, such as infection, or trauma which result in the unregulated dig ...

refers to the fact that cells do not die in a programmed and orderly way as in apoptosis.

Causes

Frequently, caseous necrosis is encountered in the foci of

tuberculosis Tuberculosis (TB) is an infectious disease usually caused by ''Mycobacterium tuberculosis'' (MTB) bacteria. Tuberculosis generally affects the lungs, but it can also affect other parts of the body. Most infections show no symptoms, in w ...

infections. It can also be caused by syphilis and certain fungi. A similar appearance can be associated with histoplasmosis, cryptococcosis, and coccidioidomycosis.

Pathophysiology

This begins as infection is recognized by the body and macrophages begin walling off the

microorganism A microorganism, or microbe,, ''mikros'', "small") and ''organism'' from the el, ὀργανισμός, ''organismós'', "organism"). It is usually written as a single word but is sometimes hyphenated (''micro-organism''), especially in olde ...

s or pathogens. 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 clump together creating soft granular mass that has the appearance of cheese. As cell death begins, the granuloma forms and cell death continues the inflammatory response is mediated by a type IV hypersensitivity reaction. Some data suggests that the epithelioid morphology and associated barrier function of host macrophages associated with granulomas may prevent effective immune clearance of mycobacteria.

Appearance

In caseous necrosis no histological architecture is preserved. On microscopic examination with H&E staining, it is characterized by acellular pink areas of necrosis surrounded by a granulomatous inflammatory process. When the hilar

lymph node A lymph node, or lymph gland, is a kidney-shaped organ of the lymphatic system and the adaptive immune system. A large number of lymph nodes are linked throughout the body by the lymphatic vessels. They are major sites of lymphocytes that inc ...

for instance is infected with tuberculosis and leads to caseous necrosis, its gross appearance can be a cheesy tan to white, which is why this type of necrosis is often depicted as a combination of both coagulative and liquefactive necrosis. However, in the lung, extensive caseous necrosis with confluent cheesy tan granulomas is typical. The tissue destruction is so extensive that there are areas of cavitation (also known as cystic spaces). See

Ghon's complex Ghon's complex is a lesion seen in the lung that is caused by tuberculosis. The lesions consist of a Ghon focus along with pulmonary lymphadenopathy within a nearby pulmonary lymph node. A Ghons complex retains viable bacteria, making them sour ...

. Image:Tuberculosis - Sub-pleural primary (Ghon) focus (6596011395).jpg, Caseous necrosis in the pleura Image:Renal tuberculosis (6539942987).jpg, Caseous necrosis in the kidney

References

External links

Microscope images of caseous necrosis

{{Pathology Histopathology Tuberculosis Necrosis