ABL1 and chronic myelogenous leukemia, BCR-ABL1 positive: Chronic myeloid leukemia (CML) is characterized by the Philadelphia chromosome (Ph), produced by the balanced reciprocal translocation t(9;22)(q34;q11) leading to the breakpoint cluster region-Abelson (BCR-ABL1) fusion gene (Hehlmann et al. 2007).