ABL1 and chronic myelogenous leukemia, BCR-ABL1 positive: The main genetic event causing CML is reciprocal translocation t (9;22)(q34;q11), or Philadelphia chromosome, causing formation of “breakpoint cluster region” (BCR)-“Abelson murine leukemia” (ABL) fusion transcript, which encodes the BCR-ABL oncoprotein with constitutively active tyrosine kinase activity [27].