RUNX1 and leukemia: However, the prevalence of detectable RUNX1–RUNX1T1 and TEL–RUNX1 in cord blood is 100-fold greater than the risk of the corresponding leukaemia, and the frequency of positive cells (10−4 to 10−3) indicates substantial clonal expansion of the abnormal progenitor population (Mori et al., 2002).