ANAPLASTIC LARGE-CELL LYMPHOMAS EXPRESSING THE NOVEL CHIMERIC PROTEINP80(NPM ALK) - A DISTINCT CLINICOPATHOLOGICAL ENTITY/

Anaplastic large cell lymphoma (ALCL) is a subtype of non-Hodgkin's ly mphoma characterized by the CD30(+) large neoplastic cells and sometim es carries a t(2;5)(p23;q35). Recently, we found a novel hyperphosphor ylated 80-kD protein tyrosine kinase, p80, in ALCLs with t(2;5). Subse quent cDNA cloning showed p80 to be a fusion protein of two genes, the novel tyrosine kinase gene and the nucleophosmin gene, in accordance with the sequence of the NPM/ALK gene (Morris et al, Science 263:1281, 1994). Meanwhile, the clinicopathologic features of p80-carrying ALCL s have remained unclear. Paraffin sections of 105 cases of ALCL were i mmunostained using anti-p80 antibody, and 30 of them were shown to exp ress p80. Clinicopathologic comparison between p80-positive and -negat ive ALCLs showed that p80-positive cases occurred in a far younger pat ient age group (16.2 +/- 12.9 years; p80-negative cases, 51.0 +/- 22.3 years; P < .0001) and the patients showed a far better 5-year surviva l rate (79.8%; p80-negative group, 32.9%; P < .01). These data showed that p80-positive ALCL is a distinct entity both clinically and pathog enetically and should be differentiated from p80-negative ALCL. (C) 19 95 by The American Society of Hematology.