An initial report demonstrated a 14% frequency of FLT3 mutations among childhood ALL overall, with mutations concentrated among the cytogenetic subgroups high hyperdiploidy (> 50 chromosomes in diagnostic karyotype) and MLL-translocation [8]; more recent studies have indicated a lower overall frequency in childhood ALL (in the 1-8% range) while consistently demonstrating a higher incidence among those with MLL rearrangement and high hyperdiploidy [9-13]. This evidence concerns the gene KMT2A and acute lymphoblastic leukemia.