Plasmablastic Lymphoma of Head and Neck: Report of Two New Cases and Correlation with c-myc and IgV_H 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.