The first study investigating the presence of RAS mutations by Sanger Sequencing in KMT2A-rearranged ALL was published 20 years ago and found no RAS mutations in these patients.27 Subsequently independent groups have reported RAS mutations in up to 80% of KMT2A-rearranged ALL and 50% KMT2A-rearranged AML (Fig. 2 and Supplemental Table 1, Supplemental Digital Content).27RAS mutations were most common in infant with KMT2A-AFF1-rearranged ALL28–30 (Fig. 2). The gene discussed is AFF1; the disease is acute lymphoblastic leukemia.