Fig. 2

A (Hematoxiline-eosin, 100X): Pericardium with diffuse fibrous thickening, with focal areas of intersecting fascicles (storiform pattern—asterisk), and fibrinous areas at the surface (arrow); B (Hematoxiline-eosin, 400X): Patchy lymphoplasmacytic infiltration, and areas with Russell bodies (arrow)—atypical plasma cells with eosinophilic, homogeneous immunoglobulin-containing inclusions in cytoplasm; C (CD138 immunostaining, 400X): CD138 membranous immunostaining demonstrating plasma cells forming clusters; D (IgG4 immunostaining, 400X): cytoplasmatic immunostaining demonstrating an increased absolute count of IgG4-positive cells (> 20 per high-power field) with a marked storiform fibrosis pattern (arrow)