Kaposi sarcoma associated herpesvirus (KSHV)/human herpesvirus 8 (HHV-8) associated “solid” lymphoma; case 1. (A) Immunohistochemistry for KSHV/HHV-8 open reading fragment 73 (ORF73) protein. The ORF73 protein is detected in the nucleus of almost all of the tumour cells (original magnification, ×40). (B) Polymerase chain reaction for KSHV/HHV-8 ORF72. A band compatible with the genomic sequence is detectable. Lane 1, DNA extracted from case 1; lane 2, DNA extracted from a positive control (CRO-AP/6 primary effusion lymphoma cell line); M, DNA molecular weight marker. (C) A lymph node infiltrated by large anaplastic cells exhibiting a sinusoid pattern of growth. Haematoxylin and eosin staining; original magnification, ×40. (D) Immunohistochemistry for cytoplasmic IgG showing that the tumour cells are positive for this antigen (original magnification, ×40). (E) Immunohistochemistry for MUM1/IRF4. All tumour cells show intense nuclear staining for MUM1/IRF4 (original magnification, ×40).