AFF1 and acute lymphoblastic leukemia: The CD34+/CD10– subset has been shown to be associated with chromosome 11 mutations involving the MLL gene.30 The most common of these translocations is t(4;11) (MLL-AF4), present in 5% of ALL.18 Our finding of a 6% prevalence of the CD34+/CD10– phenotype is consistent with this.