ACUTE LYMPHOID LEUKEMIAS FOLLOWING EITHER A PREVIOUS CHRONIC MYELOGENOUS LEUKEMIA OR MYELODYSPLASTIC SYNDROME - PHENOTYPIC AND GENOMIC DIFFERENCES

We have analyzed the immunological and genomic characteristics of the lymphoid blast cells present in secondary lymphoid leukemias following either a previous chronic myelogenous leukemia (CML) or myelodysplast ic syndrome (MDS). Twenty-one of 107 secondary leukemias analyzed disp layed a lymphoid phenotype (15 after a CML and 6 after a MDS). Most of the lymphoid blast crises of CML (73%) correspond to pure lymphoid tr ansformation, all of them having a common acute lymphoblastic leukemia (ALL) phenotype (CD10+). By contrast, in all MDS cases, lymphoid blas t cells coexisted with another myeloid component (hybrid leukemias) an d showed an early B phenotype. IgH and TCR-gamma gene rearrangements w ere detected in the CML-lymphoid blast crisis (86% of cases) more freq uently than in the MDS transformations (33%). The TCR-beta gene was in germ line configuration in all cases while TCR-delta gene rearrangeme nts were detected in four cases, all of them corresponding to a previo us diagnosis of CML. These results show the existence of both immunoph enotypic and genomic differences between the lymphoid transformations of either CML or MDS, which could reflect differences at the stage of maturation of the target cell in these transformations. (C) 1993 Wiley -Liss, Inc.