HIGH-INCIDENCE OF THE T(2-5)(P23-Q35) TRANSLOCATION IN ANAPLASTIC LARGE-CELL LYMPHOMA AND ITS LACK OF DETECTION IN HODGKINS-DISEASE - COMPARISON OF CYTOGENETIC ANALYSIS, REVERSE TRANSCRIPTASE-POLYMERASE CHAIN-REACTION, AND P-80 IMMUNOSTAINING

Fifty-six cases of anaplastic large cell lymphoma (ALCL), 23 cases of Hodgkin's disease, and 16 cases of diffuse large cell lymphoma were in vestigated for the t(2;5)(p23;q35) translocation. The translocation wa s detected by using cytogenetic analysis, reverse transcriptase-polyme rase chain reaction (RT-PCR) and immunohistochemistry with P80 antibod y directed against the kinase domain of anaplastic lymphoma kinase (AL K) of the chimeric NPM/ALK protein. In all but three cases of ALCL, we found an agreement between cytogenetic analysis, RT-PCR, and P80 stai ning. However, in one case, the t(2;5) translocation was detected with cytogenetic analysis, but RT-PCR and P80 staining were found to be ne gative. Conversely, in another case the karyotype was normal, but the hybrid mRNA and P80 staining were found to be positive. In one case, m alignant cells showed a translocation involving chromosomes 1q25 and 2 p23 and were strongly positive for P80 staining. Such a result could b e expected because P80 antibody detects the kinase domaine of the ALK protein encoded by chromosome 2p23. Overall 73.2% (41 of 56) of cases were found to be positive. However, the highest percentage (23 of 26 c ases; 88.5%) of P80 positive cases was found in children compared with 60% (18 of 30 cases) in adult ALCL (P <.05). In Hodgkin's disease, Re ed-Sternberg cells were found to be clearly negative by RT-PCR and wit h P80 antibody. The latter results suggest that Hodgkin's disease and t(2;5)-positive ALCL are distinct biological entities and that the dem onstration of the t(2;5) translocation is of diagnostic importance in differentiating these two entities. The results of the present study i ndicate that immunohistochemistry with P80 antibody is a reliable meth od for detecting NPM/ALK chimeric protein. (C) 1996 by The American So ciety of Hematology.