Flow cytometric evidence for minimal residual disease and cytological heterogeneities in acute lymphoblastic leukemia with severe hypodiploidy.

Abstract

Two subpopulations of small and large leukemia cells and binucleated cells were present in the bone marrow of a 10-year-old girl with acute lymphoblastic leukemia (ALL). Cytogenetic studies showed some cells with a karyotype of 34,X,-X,-2,-3,-4,-5,-7,-9,-13,-15,-16,-17,-20, and others with a karyotype that was exactly double the chromosome set in the cells with 34 chromosomes. Flow cytometric (FCM) examination of surface common ALL antigen (CALLA) and DNA content of the lymphoblasts led to the identification of the primary hypodiploid DNA stemline (DI = 0.72), which corresponds to the small-sized blasts, and the secondary hyperdiploid DNA stemline (DI = 1.44), which corresponds to the large-sized blasts. Sequential bone marrow examinations with FCM and cytogenetics revealed the persistence of the primary hypodiploid clone during remission and their proliferation with chromosomal evolution at full relapse. These results suggest that more rational inductive therapy should be designed to achieve the favorable outcome of ALL with severe hypodiploidy and that FCM is a useful tool to monitor the minimal residual disease of this subgroup in ALL.