For children with B-ALL, cytogenetically aberrant cells are present in the CD34+, CD33−, CD38−, CD19− primitive cell compartment in the bone marrow (BM), and engraftment of B-ALL into NOD/SCID mice was achieved with CD34+, CD10− cells or CD34+, CD19− cells (Quijano et al., 1997; Cox and Blair, 2005; Hirt et al., 2011). Here, CD34 is linked to precursor B-cell acute lymphoblastic leukemia.