Plasmablastic lymphoma of head and neck: report of two new cases and correlation with c-myc and IgVH gene mutation status.

Plasmablastic lymphoma (PBL) is a rare acquired immunodeficiency syndrome-associated non-Hodgkin's lymphoma (AIDS-NHL), with predilection for the mucosa of oral cavity. It usually has a plasmablastic morphology, expressing plasma cell-associated antigens with weak or absent expression of B-cell-associated markers. To further define the immunophenotypic and molecular genetics of these tumors, we investigated two cases of plasmablastic lymphomas of the head and neck for c-myc gene rearrangement and immunoglobulin heavy chain (IgV(H)) hypermutation status. For the first time we report a case of AIDS-related PBL that, by fluorescence in situ hybridization (FISH), shows a c-myc gene rearrangement. Although current literature suggests that most cases of c-myc gene rearranged AIDS-NHL are Burkitt's lymphoma, our case has an immunophenotype characteristic for PBL. In this case, IgV(H) hypermutation analysis showed a somatic hypermutation, indicative of germinal center transit. The concurrent B-cell immunophenotype of BCL-6(-)/CD138(+)/MUM-1(+) also suggests a post-germinal center B-cell origin of this lymphoma. The immunophenotype of our second case (BCL-6(-)/CD138(+)/MUM-1(+)) also suggests a post-germinal center B-cell origin. However, IgV(H) hypermutation analysis was not possible in this case.