We present common cytogenetic features in the largest cohort of plasmablastic lymphoma (PBL) of the
oral cavity published to date. This cohort included 45 patients, 32 of whom had a known HIV status, of
which 31 were HIV positive. Ninety eight per cent of all PBL cases were known to be EBV positive. In line
with previous studies, we found that rearrangements of the MYC gene was the most common genetic
abnormality seen in 60% of cases with the immunoglobulin heavy chain (IGH) locus as a partner in
51% of cases. Additional complex genetic aberrations were frequent, in particular, an increased copy
number of the CCND1 gene was seen in 41% of cases with true amplification of CCND1 in 15% of cases.
Aneuploidy was also observed for the BCL6 gene in 28% of cases. Interestingly, rearrangements of both
IGH genes were detected in 16% of cases with t(14;18) and t(11;14) respectively involved in conjunction
with a t(8;14) in two cases. These bi-allelic IGH rearrangements have not been described before in oral
PBL. Our results reinforce the notion that EBV infection and MYC rearrangements are important events
in the pathogenesis of oral PBL. The genetic diversity and complexity observed in these cases, underlines
the importance to genetically characterise PBL patients at presentation as this may inform the choice of
more effective treatment modalities.