First, Weir et al. [86] designed and validated a protocol using red blood cell-lysed bone marrow samples and two four-color antibody combinations (CD19/CD45/CD20/CD10 & CD19/CD45/CD9/CD34), allowing MRD assessment with a sensitivity of 0.01% in 99% of the BCP-ALL patients. This evidence concerns the gene CD9 and acute lymphoblastic leukemia.