AIDS-PCNSL. (A) BCL-6 protein expression in a case of AIDS-PCNSL (diffuse large cell lymphoma). The microphotograph shows that the tumor is relatively monomorphous and consists of large tumor cells displaying a large noncleaved cell morphology. In this field, nuclear positivity for BCL-6 is present on several tumor cells. Paraffin-embedded tissue section, APAAP immunostaining, hematoxylin counterstain. (B) LMP-1 expression in a case of AIDS-PCNSL (diffuse large cell lymphoma). The microphotograph shows that the tumor is polymorphous and consists of large tumor cells displaying an immunoblastic-plasmacytoid morphology. LMP-1 positivity is manifested as cytoplasmic or membrane staining on some large tumor cells. Paraffin-embedded tissue section, APAAP immunostaining, hematoxylin counterstain. Original magnification ×400 (A) and (B).