Cytogenetic analysis is an important aid in the classification of hematological disorders. Most types of leukemia display either numerical chromosomal abnormalities or structural rearrangements, mainly translocations. Nonrandom chromosomal abnormalities, which are being increasingly recognized, are especially useful in diagnosing the leukemic subtype and predicting treatment outcome. Molecular analysis of genes adjacent to the breakpoints of specific translocations and the study of the functions of their gene products have helped to clarify the complex interactions that promote leuke-mogenesis and perpetuate the leukemic phenotype (1 ).
