CML, primarily induced by the expression of an abnormal BCR/ABL fusion tyrosine kinase, is characterized by a gradual progression from a benign chronic phase displaying hyperproliferation of normally maturing myeloid cells to a lethal blast crisis, in many cases resembling AML where myeloid differentiation is impaired. This evidence concerns the gene BCR and chronic myelogenous leukemia, BCR-ABL1 positive.