What type of necrosis is characteristic of caseating granulomas seen in tuberculosis?

• A. Liquefactive necrosis
• B. Coagulative necrosis
• C. Fibrinoid necrosis
• D. Caseous necrosis

Answer: (D)

Tuberculosis forms granulomas with a central area of necrosis that has a cheese-like appearance, known as caseous necrosis. This results from the activated macrophages and T-helper 1–mediated immune response that drives cell death within the granuloma, leaving a soft, granular, acellular debris. Grossly the center looks pale, crumbly, and friable, which is the hallmark feature. Other patterns of necrosis don’t fit this setting: liquefactive necrosis creates a liquid, pus-filled center typical of abscesses; coagulative necrosis preserves tissue architecture and is more common with ischemia; fibrinoid necrosis involves fibrin deposition in vessel walls seen in certain vasculitides.