Recent genome-wide studies have provided critical pathogenetic insights into paediatric BCP ALL, including the identification of a dismal prognosis for cases with IKZF1 deletions2, 3, 4, 5 and for cases with a ‘Ph-like'4, 5, 6, 7, 8 gene-expression signature similar to that of Philadelphia (Ph)-positive ALL. Here, IKZF1 is linked to acute lymphoblastic leukemia.