BCR and chronic myelogenous leukemia, BCR-ABL1 positive: Chronic myeloid leukaemia (CML) is a stem cell disease characterized by a unique cytogenetic marker, the Philadelphia (Ph) chromosome, arising from the reciprocal translocation between the long arm of chromosomes 9 with the Abelson1 (ABL1) oncogene juxtaposed to the breakpoint cluster region (BCR) gene on chromosome 22 t(9;22) (q34;q11) [1,2,3,4].