The final diagnosis of EBV-positive DLBCL was confirmed based on the expression of B-cell-specific transcription factors (Oct-2 and BOB.1), PCR-based identification of monoclonal rearrangement of the immunoglobulin genes, and the presence of EBV-encoded small RNAs in the tumor cells (identified using in situ hybridization).
Interestingly, there were several normal (eg germinal centre centroblasts and monocytoid B-cells) and malignant B-cell populations (eg a proportion of diffuse large B-cell lymphomas, DLBCLs) that were Ig-negative, despite their BOB.1/OBF.1 and Oct2 expression.
In addition to their different clonal origin, Reed-Sternberg cells of Hodgkin's disease expressed a CD15+, CD20+ (rare cells), CD30+, Oct-2-, EBNA2-, LMP1+ phenotype, whereas anaplastic and Reed-Sternberg-like cells of diffuse large B-cell lymphoma were CD15-, CD20+, CD30+, Oct-2+, EBNA2+, and LMP1+.