Giant Cell Arteritis
General: A granulomatous form of ANCA-negative large vessel vasculitis. The most common vasculitis in patients >50 years old.
Gross: Typically involves the aorta and its major branches, especially extracranial arteries. Has segmental involvement, thus a 3 cm long segment should be sectioned and submitted entirely for histologic examination; the most abnormal areas should be focused upon (indurated, painful, etc.).
Microscopic: Mononuclear cell infiltrate composed primarily of macrophages and lymphocytes, originating in the media and extending to the intima and adventitia of large vessels. Multinucleated giant cells (Langerhans or foreign body type) are seen in only ~50% of cases, often adjacent to the fragmented internal elastic lamina. Fibrinoid vascular wall necrosis is uncommon and patchy if present; may represent another type of ANCA-negative vasculitis. Has segmental involvement, thus may not be seen in all sections.
Differential Diagnosis:
- Polyarteritis nodosa: involves medium-sized vessels
Stains:
- Positive:
- Negative:
- Suggested, focused panel:
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Images:
Cases:
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