ABL1 and chronic myelogenous leukemia, BCR-ABL1 positive: The BCR/ABL fusion protein is encoded by the fusion gene generated by a reciprocal t(9;22) (q34;q11.2) chromosomal translocation causing the Philadelphia chromosome (Ph), which is the molecular signature of chronic myeloid leukemia (CML) and is also observed in 30–40% of ALL (12,13).