In the more recent years, the “targeted” therapy has became a reality even in hematology: in the chronic myeloid leukemia, the management of patient and the eventual switch to a second or third tyrosine-kinase inhibitor is leaded by the assessment of the BCR-ABL1/ABL1 ratio and by the demonstration of mutations in the tyrosine domain of ABL1, as defined by the European Leukemia Network guidelines (Baccarani et al., 2013). Here, BCR is linked to chronic myelogenous leukemia, BCR-ABL1 positive.