Defined by a similar GEP to Ph + B-ALL, but in the absence of the BCR-ABL1 rearrangement [t(9;22)]. Rearrangements in CRLF2 or EBF1-PDGFRB, as well as concurrent JAK mutations, and/or IKZF1 (Ikaros) deletions/mutations may be seen. Here, CRLF2 is linked to acute lymphoblastic leukemia.