ALK-positive plasmablastic B-cell lymphoma with expression of the NPM-ALK

While most anaplastic lymphoma kinase (ALK)–positive non-Hodgkin lymphomas (NHLs) are of T-cell lineage, a small num-ber of B-lineage tumors with plasmablas-tic morphology and expression of the full-length ALK protein have been de-scribed in the literature. All of these re-ported tumors lacked the NPM-ALK fu-sion transcript. There is controversy regarding the existence of ALK fusion– positive B-cell NHL, with many investiga-tors contending that ALK fusions are expressed uniquely in T- or null-cell lym-phomas. Here we describe 2 well-charac-terized cases of ALK-positive B-cell lym-phoma expressing the NPM-ALK fusion. Both tumors occurred in pediatric pa-tients and showed poor response to che-motherapy. Each had plasmablastic mor-phology, showed immunoglobulin A restriction, and was ALK positive and CD30 by immunohistochemistry. One tu-mor showed the t(2;5)(p23;q35) chromo-somal translocation by conventional cyto-genetics. Both were positive for NPM-ALK by reverse transcriptase–polymerase chain reaction. Thus, ALK-positive plas-mablastic B-cell lymphomas are more het-erogeneous at the molecular level than previously recognized. (Blood. 2003;102