The consideration of interstitial deletion/recombination events in two (or more) size classes is supported by other studies showing that micro-deletions are a general feature of human T-ALL [66], and that recurrent focal deletions (such as observed here in Notch1, Cdkn2a, Ikzf1 and Pten) are likely the result of illegitimate recombination events [67] rather than the repair of radiation-induced DNA damage. Here, NOTCH1 is linked to acute lymphoblastic leukemia.