Histopathology of PEL and MCD. (A) PEL cells are large, with pleomorphic immunoblastic/plasmablastic features. A mitotic figure indicates proliferation of the tumor cells. Immunostaining of a cytospin preparation (insert) with an antibody to LANA shows the characteristic dot pattern in the nucleus (modified Giemsa stain, ×100 original magnification; insert: immunoperoxidase, ×100 original magnification). (B) Follicles in KSHV⁺ MCD are often involuted and hyalinized. There are many plasma cells in the interfollicular area and prominent vascular proliferation. In addition, a number of KSHV⁺ plasmablasts (arrows; insert) are present in mantle cell zones. These plasmablasts are LANA⁺ and vIL-6⁺ (hematoxylin and eosin [H&E] and immunoperoxidase staining, ×20 original magnification; inserts: ×60 original magnification).