DENND1B and acute lymphoblastic leukemia: The importance of the novel in-frame gene fusions in the remaining five cases remains to be determined, but it is noteworthy that three had fusions (DENND1B-ZCCHC7, MEF2D-FOXJ2, IKZF1-NUTM1) involving genes recurrently rearranged in BCP ALL, namely ZCCHC7, MEF2D, IKZF1 and NUTM1 (ref. 24).