Although the t(8;21) translocation encodes an oncoprotein that, in combination with co‐occurring mutations, drives leukaemogenesis, AML with t(8;21)/RUNX1–RUNX1T1 exhibits distinct developmental stages of leukaemic cells, as revealed by immunophenotypic stratification. The gene discussed is RUNX1T1; the disease is acute myeloid leukemia.