KMT2A and acute lymphoblastic leukemia: ALL cannot be determined from morphology alone and further diagnostic testing such as flow cytometry is required to define B- or T-cell lineage ALL [23], and karyotyping and fluorescence in situ hybridization (FISH) to assess gross chromosomal abnormalities and specific chromosomal translocations, duplications, or deletions (e.g.: ABL-class, KMT2A-rearrangements).