DETECTION OF T(2-5)(P23-Q35)-TRANSLOCATION BY REVERSE-TRANSCRIPTASE POLYMERASE CHAIN-REACTION AND IN-SITU HYBRIDIZATION IN CD30-POSITIVE PRIMARY CUTANEOUS LYMPHOMA AND LYMPHOMATOID PAPULOSIS

The t(2;5) generates a chimeric NPM-ALK transcript encoded by the nucl eophosmin NPM gene fused to the anaplastic lymphoma kinase gene ALK. U sing a reverse transcriptase nested polymerase chain reaction assay, w e have detected NPM-ALK transcripts within CD30(+) primary cutaneous l ymphoma and lymphomatoid papulosis (LP). The t(2;5) was identified in 4 out of 9 CD30(+) anaplastic lymphomas and in 1 out of 4 CD30(+) pleo morphic lymphomas. Moreover, the t(2;5) was detected in 3 out of 10 LP s. All NPM-ALK-positive lymphomas and 1 NPM-ALK-positive LP exhibited a clonal rearrangement of the T cell receptor gamma-chain gene. The t( 2;5) was detected in 2 cases of LP without other evidence for a clonal lymphoid population. To identify cells carrying the t(2;5) translocat ion, we used immunohistochemistry to detect the ALK-encoded p80 protei n and in situ hybridization for the specific detection of NPM-ALK tran scripts. Both p80 protein and NPM-ALK transcripts were expressed by an aplastic or large CD30(+) lymphoma cells with positive NPM-ALK amplifi cation. The presence of t(2;5) in a subset of CD30(+) cutaneous lympho ma LP may indicate a common pathogenesis with a subset of anaplastic n odal lymphoma.