Interestingly, a subtype of B-ALL defined by a t(1;19) chromosomal translocation that generates the oncogenic fusion protein E2A-PBX1, revealed uniform (4/4) expression of cell surface ROR1, whereas only a small fraction (2/35) of t(1;19)-negative cases were positive [18]. Here, PBX1 is linked to acute lymphoblastic leukemia.