CML is a myeloproliferative disorder resulting from the oncogenic transformation of hematopoietic stem cells, and is characterized by the Philadelphia chromosome, a reciprocal translocation between the exon 2 sequence upstream of the Abelson murine leukemia (ABL) proto-oncogene on chromosome 9 and the 5′ sequence of the breakpoint cluster region (BCR) gene on chromosome 22. This evidence concerns the gene ABL1 and chronic myelogenous leukemia, BCR-ABL1 positive.