AIDS-related PCNSL (DLCL). Two-color staining. (A) In this microphotograph, several tumor cells exhibit nuclear staining (blue) for BCL-6 and few cells show a strong cytoplasmic and membrane staining (reddish) for LMP-1. No coexpression of both markers by the same tumor cell is detectable. (B) Microphotograph of a different field in which there is a prevalence of LMP-1⁺ cells with few BCL-6⁺ nuclei. No coexpression is detectable. Paraffin-embedded tissue section, no counterstain. Original magnification × 400.