The specimen received consisted of a portion of dura that was expanded by a mixed inflammatory infiltrate as well as a small fragment of adherent cerebral cortex. On low-power view the dura was thickened and fibrotic with a slightly nodular architecture (Fig. 2). Closer inspection revealed a mixed inflammatory infiltrate composed predominantly of lymphocytes and plasma cells, but also containing neutrophils (Fig. 3). Interspersed and occasionally in sheets were large, plump, pale histiocytes with abundant finely vacuolated cytoplasm and eccentric nuclei. Scattered histiocytes showed unequivocal intracytoplasmic lymphocytes and/or neutrophils (emperipolesis) (Fig.4). Immunohistochemistry for S-100 protein showed strong cytoplasmic staining of histiocytes and highlighted emperipolesis (Fig 5). Histiocytes were negative for CD1a. Immunostains for B (CD20) and T cells (CD3) demonstrated a mixed inflammatory infiltrate. Stains for organisms (AFB and GMS) were negative.