What histologic feature is characteristic of granulomatous inflammation?

What histologic feature is characteristic of granulomatous inflammation?

• A. Diffuse neutrophilic infiltration
• B. Lymphoid follicles
• C. Aggregates of epithelioid macrophages with possible giant cells, often with caseation
• D. Fibrosis

Answer: (C)

Granulomatous inflammation is a chronic form of inflammation organized into nodular collections driven by activated macrophages. The defining histologic feature is aggregates of epithelioid macrophages—these macrophages have a modified, elongated appearance that resembles epithelial cells. They often fuse to form multinucleated giant cells. In many classic granulomas, especially those due to tuberculosis or certain fungal infections, the center may undergo caseation necrosis, producing a cheese-like core. A surrounding rim of lymphocytes and sometimes fibroblasts reflects the T-cell–mediated immune response that activates macrophages via IFN-γ. This pattern stands in contrast to diffuse neutrophilic infiltration seen in acute inflammation, solitary lymphoid follicles that indicate lymphoid tissue activity, or fibrosis that represents scar formation rather than organized granuloma formation.

Granulomatous inflammation is a chronic form of inflammation organized into nodular collections driven by activated macrophages. The defining histologic feature is aggregates of epithelioid macrophages—these macrophages have a modified, elongated appearance that resembles epithelial cells. They often fuse to form multinucleated giant cells. In many classic granulomas, especially those due to tuberculosis or certain fungal infections, the center may undergo caseation necrosis, producing a cheese-like core. A surrounding rim of lymphocytes and sometimes fibroblasts reflects the T-cell–mediated immune response that activates macrophages via IFN-γ. This pattern stands in contrast to diffuse neutrophilic infiltration seen in acute inflammation, solitary lymphoid follicles that indicate lymphoid tissue activity, or fibrosis that represents scar formation rather than organized granuloma formation.