Histologic sections of the submitted dura showed permeation by a dense, diffuse (Fig. 1) and focally nodular (Fig. 2) granulomatous infiltrate composed of histiocytes, lymphocytes, plasma cells, scattered multinucleate giant cells (arrows), eosinophils and neutrophils (Figs 1, 2). The polymorphous infiltrate showed no cytologic features of malignancy. In several areas the granulomatous infiltration was clearly vasocentric (Fig. 3) and focally small blood vessels showed fibrinoid necrosis with intramural neutrophils and karyorrhectic debris (Fig 4), and petechial hemorrhage (Fig. 5). An elastic tissue stain (Verhoeff-van Gieson) showed fragmentation of the elastica (Fig 6), confirming the impression of a vasculitic granulomatous process. Special stains for bacteria, mycobacteria, and fungi were negative.