Immunohistochemical, molecular, and cytogenetic analysis of a consecutive series of 20 peripheral t‐cell lymphomas and lymphomas of uncertain lineage, including 12 Ki‐I positive lymphomas

: Although several independent series of non-Hodgkin's lymphomas (NHLs) have been subjected to cytogenetic studies or analyses of lineages by assaying for clonal immunophenotypes and clonal rearrangements affecting immunoglobulin (IG) and T-cell receptor (TCR) genes, no published reports exist of series of non-B-cell NHLs on which cytogenetic, immunohistochemical, and IG and TCR gene rearrangement studies have been undertaken together. Among 343 NHLs ascertained prospectively between January 1984 and December 1988 at the Memorial Sloan-Kettering Cancer Center, 278 cases with clonal chromosome abnormalities were identified. Of the latter, 20 were non-B-cell NHLs, which in turn comprised 15 peripheral T-cell lymphomas (PTCLs) and 5 lymphomas of uncertain lineage (LULs). The LULs either were biogenotypic, had discordant immunophenotype and immunogenotype, or showed no evidence of B-cell, T-cell, or histiocytic derivation. Of the 15 PTCLs, eight expressed the Ki-1 antigen and four of these had translocations involving the band 5q35 [t(5q35)]. Of the five LULs, four expressed the Ki-1 antigen and one of these had a translocation involving band 5q35. Previous studies have associated t(5q35) with Ki-1 positive NHLs characterized histologically by a pleomorphic diffuse large cell morphology. In our series of 12 Ki-positive non-B-cell NHLs, five (42%) had a 5q35 translocation. They were histologically indistinguishable from the subset without the translocation. The frequent lineage uncertainty exhibited by Ki-1 positive NHLs of similar histology and cytogenetic abnormalities suggests their derivation from an early uncommitted lymphoid cells.