ABL1 and chronic myelogenous leukemia, BCR-ABL1 positive: On the other hand, the Ph-positive MPN chronic myeloid leukemia (CML) is caused by the constitutively-activated fusion tyrosine kinase BCR/ABL generated by a reciprocal t(9;22) (q34;q11.2) chromosomal translocation causing Ph, which also plays a critical role in pathogenesis of 30–40% of acute lymphoblastic leukemia (ALL) [12].