However, NUP98:NSD1 fusions occur frequently in pediatric AML and are associated with poor prognosis (84), an NUP98:ASH1L fusion was recently identified by optical gene mapping in secondary AML (85), and ASH1L also appears to play a role in leukemia driven by MLL1:AF9 fusion (86). This evidence concerns the gene MLLT3 and leukemia.