Plasmablastic lymphoma (PBL) is an aggressive lymphoma characterized by a terminally differentiated B-cell phenotype that usually occurs in immunocompromised or elderly patients. Although the clinical and pathological characteristics of these tumours have been defined the genetic alterations involved in their pathogenesis are not well known. In this study we have investigated the chromosomal alterations of MYC, BCL2, BCL6, MALT1, PAX5, and IGH loci using fluorescence in situ hybridization (FISH) in 42 plasmablastic lymphomas (PBL) and 3 extracavitary primary effusion lymphomas (PEL). MYC rearrangements were identified in 20 of 41 (49%) PBL and the immunoglobulin (IG) genes were the partners in most tumours. MYC rearrangements were more common in EBV-positive (14 of 19, 74%) than EBV-negative (9 of 21, 43%) tumours (p < 0.05). No rearrangements of BCL2, BCL6, MALT1 or PAX5 were detected in any PBL but gains of these loci were observed in 31-41% of the cases examined. Twelve of the 40 PBL in which 3 or more loci could be investigated had multiple simultaneous gains in 3 or more loci. No differences in the survival of the patients according to MYC were observed but the four patients with the longest survival (>50 months) had no or low number of gains (<3). No rearrangements of any of these loci were seen in PEL. In conclusion, PBL are genetically characterized by frequent IG/MYC translocations and gains in multiple chromosomal loci. The oncogenic activation of MYC in these lymphomas may be an important pathogenetic element associated with EBV infection.

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