Fig. 2. Pathological findings of a 36-year-old male patient (Case 1). A: The first case shows a well demarcated extra-axial dura-based mass (H&E, ×12). B: High power view shows neoplastic meningothelial proliferation with many areas of plasmacytic infiltration (H&E, ×200). C: In addition, the meningothelial cells show EMA immunoreactivity (EMA, ×100). D and E: On immunohistochemistry, a high IgG4 (IgG4, ×100)/IgG (IgG, ×100) ratio is noted.