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 production, ...

', 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 dige ...

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

apoptosis Apoptosis (from grc, ἀπόπτωσις, apóptōsis, 'falling off') is a form of programmed cell death that occurs in multicellular organisms. Biochemical events lead to characteristic cell changes (morphology) and death. These changes incl ...

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 ...

infections. It can also be caused by

syphilis Syphilis () is a sexually transmitted infection caused by the bacterium ''Treponema pallidum'' subspecies ''pallidum''. The signs and symptoms of syphilis vary depending in which of the four stages it presents (primary, secondary, latent, an ...

and certain fungi. A similar appearance can be associated with

histoplasmosis Histoplasmosis is a fungal infection caused by ''Histoplasma capsulatum''. Symptoms of this infection vary greatly, but the disease affects primarily the lungs. Occasionally, other organs are affected; called disseminated histoplasmosis, it can ...

cryptococcosis Cryptococcosis is a potentially fatal fungal infection of mainly the lungs, presenting as a pneumonia, and brain, where it appears as a meningitis. Cough, difficulty breathing, chest pain and fever are seen when the lungs are infected. When the ...

, and

coccidioidomycosis Coccidioidomycosis (, ), commonly known as cocci, Valley fever, as well as California fever, desert rheumatism, or San Joaquin Valley fever, is a mammalian fungal disease caused by ''Coccidioides immitis'' or ''Coccidioides posadasii''. Coccidio ...

Pathophysiology

This begins as infection is recognized by the body and

macrophage Macrophages (abbreviated as M φ, MΦ or MP) ( el, large eaters, from Greek ''μακρός'' (') = large, ''φαγεῖν'' (') = to eat) are a type of white blood cell of the immune system that engulfs and digests pathogens, such as cancer cel ...

s 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 In biology, a pathogen ( el, πάθος, "suffering", "passion" and , "producer of") in the oldest and broadest sense, is any organism or agent that can produce disease. A pathogen may also be referred to as an infectious agent, or simply a germ ...

. 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

granuloma A granuloma is an aggregation of macrophages that forms in response to chronic inflammation. This occurs when the immune system attempts to isolate foreign substances that it is otherwise unable to eliminate. Such substances include infectious ...

s 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

tous 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 inclu ...

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 sources ...

. Image:Tuberculosis - Sub-pleural primary (Ghon) focus (6596011395).jpg, Caseous necrosis in the

pleura The pulmonary pleurae (''sing.'' pleura) are the two opposing layers of serous membrane overlying the lungs and the inside of the surrounding chest walls. The inner pleura, called the visceral pleura, covers the surface of each lung and dips bet ...

Image:Renal tuberculosis (6539942987).jpg, Caseous necrosis in the kidney

References

External links

Microscope images of caseous necrosis

{{Pathology Histopathology Tuberculosis Necrosis