What histologic feature characterizes giant cell arteritis?

• A. Neutrophilic infiltration
• B. Fibrinoid necrosis
• C. Granulomatous inflammation with multinucleated giant cells
• D. Lymphocytic infiltration

Answer: (C)

Granulomatous inflammation with multinucleated giant cells in the media of large- to medium-sized arteries is the histologic hallmark of giant cell arteritis. In affected vessels, you see macrophages forming granulomas with Langhans-type multinucleated giant cells, often accompanied by lymphocytes and destruction or fragmentation of the internal elastic lamina, which drives intimal thickening and luminal narrowing. This pattern is what sets giant cell arteritis apart from conditions with neutrophilic infiltration (acute vasculitis), fibrinoid necrosis (immune-complex–mediated or polyarteritis nodosa–type processes), or pure lymphocytic infiltration (which lacks the granulomatous giant cell reaction).