Double stainings in the interfollicular area of normal tonsil.

(A,C) Paraffin sections. (B) Frozen section. (A) A large cell coexpressing surface CD30 (blue) and nuclear MUM1 (brown) is indicated by the arrow; a MUM1⁺/CD30⁻ small cell is also observed (arrowhead) (× 1000; no counterstain). (B) A large cell coexpressing surface CD30 (red) and nuclear MUM1 (brown) is indicated by the arrow (× 1000; hematoxylin counterstain). (C) Many large cells in the area adjacent to the follicle mantle (most likely CD30⁺ cells) coexpress the proliferation antigen Ki67 (blue labeling of nucleoli) and the brown nuclear MUM1 protein (double arrowheads). Arrowhead indicates a Ki67⁺/MUM1⁻ cell. Arrow indicates a Ki67⁻/MUM1⁺ cell (× 800 ; no counterstain).