In the setting of chronic myeloid leukemia (CML), which is invariably associated with BCR-ABL1 translocations (the so-called Philadelphia chromosome), MRD is classically monitored by RQ-PCR, which has been highly standardized across worldwide laboratories, and its prognostic role has fully been integrated with tyrosine kinase inhibitors (TKIs)-based therapeutic management. This evidence concerns the gene BCR and chronic myelogenous leukemia, BCR-ABL1 positive.