BCR and chronic myelogenous leukemia, BCR-ABL1 positive: One of the main characteristics of chronic myeloid leukemia (CML) is the occurrence of a reciprocal translocation called the Philadelphia chromosome (Ph+), which is formed by the fusion of the 3′ sequences of the ABL1 gene (Abelson) mapped at 9q34 with the 5′ portion from the sequences of the BCR gene (breakpoint cluster region) located at 22q11, giving rise to a chimeric gene called BCR-ABL, t(9;22)(q34;q11.2), which is used in clinical CML as a diagnostic marker, and also for monitoring and prognosis [1,2].