(A), (B), and (D) Hodgkin's disease, nodular sclerosis subtype. Variants of the RS cell (the lacunar cells) show cytoplasmic and membrane staining of variable intensity for B-B4 antibody (arrows) both in frozen (A ) and in Bouin-fixed paraffin-embedded tissue sections (B) and (D). (C) Hodgkin's disease, mixed cellularity subtype. RS cells of classical type show cytoplasmic and membrane staining for B-B4 antibody (arrows) in frozen (C, [C inset]) sections. (E) A mononuclear variant of the RS cell displays homogeneous cytoplasmic staining in a Bouin-fixed paraffin-embedded tissue section. Note positive staining of bystander plasma cells (asterisks) (A), (B), and (C). (F ) Hodgkin's disease, nodular sclerosis subtype. Frozen section. Sclerosis-trapped spindle cells show intense staining for B-B4 antibody (top left). APAAP immunostaining; hematoxylin counterstain. Original magnification × 250 (A), (C); × 400 (B), (C inset), (D), (E), and (F ).