ABL1 and acute lymphoblastic leukemia: Initially, the DNA index of each patient sample is measured by flow cytometry, and the samples are screened for selected ALL fusions (i.e., TCF3-PBX1, ETV6-RUNX1, MLL rearrangement, and BCR-ABL1) by RT-PCR and fluorescence in situ hybridization (FISH) (Figure 1).