BCR and precursor B-cell acute lymphoblastic leukemia: In support of this, 80% of cells in the day 567 cerebrospinal fluid (CSF) sample from patient 1703 were leukemic blasts (CD10+, CD19+, CD45low/−), while RNA-derived clonotypic B-ALL sequences represented only 3.38% of all BCR sequences (Supplementary Table S7).