PBX1 and leukemia: This has been the subject of recent reviews [52,53], but in brief, the ETV6-RUNX1 and TCF3-PBX1 fusions have been detected in DBSs in up to 5% and 0.6% of healthy newborns, respectively, frequencies much higher than the incidences of these leukemia subtypes, thus supporting that additional mutations are required for progression to overt leukemia.