KMT2A and acute lymphoblastic leukemia: While MLL aberrations most frequently occur in the form of chromosomal rearrangements leading to the production of chimeric fusions, partial tandem duplications, and internal exonic deletions, studies have revealed amplification of the associated genomic region without characteristic MLL rearrangements in approximately 1% of AML and rare cases of myelodysplastic syndrome, as well as acute lymphoblastic leukemia (Greaves and Wiemels, 2003, Yip and So, 2013).