Although the number of MEF2D-rearranged cases was small compared with several other subtypes, analysis of children with ALL enroled on the AALL0232 study of high-risk pre-B ALL showed that the 5-year event-free survival (EFS) of MEF2D-rearranged ALL was 71.6% (s.e.±10.2%, n=22), compared with that of BCR-ABL1 (59.9±8.9%, n=48), MLL (77.5±10.6%, n=25), Ph-like (60.3±5.5%, n=115) and other pre-B ALL cases (87.3±1.6%, n=612; log rank test P<0.0001; Fig. 3). The gene discussed is ABL1; the disease is acute lymphoblastic leukemia.