Chronic myeloid leukemia (CML) is a myeloproliferative neoplasm characterized by fusion of the Abelson murine leukemia (ABL) gene on chromosome 9 with the breakpoint cluster region (BCR) gene on chromosome 22, which results in the expression of an oncoprotein, termed BCR-ABL1 tyrosine kinase [1–3]. The gene discussed is BCR; the disease is chronic myelogenous leukemia, BCR-ABL1 positive.