The fourth AML-RGA case (case 187) was a 10-year-old boy with AML with t(8;21)(q22;q22.1); RUNX1T1::RUNX1, which interestingly showed myelomastocytic differentiation with increased serum tryptase (29 μg/L) and two KIT mutations (c.1251_1266delins16 and c.2466 T > A (p.Asn822Lys)), which have not been described in systemic mastocytosis. This evidence concerns the gene RUNX1 and acute myeloid leukemia.