Colony progenitor assays have confirmed the early acquisition of mutant EZH2 in a patient with CMML who carried two TET2 mutations in addition to an EZH2 mutation [20] and in three patients with atypical CML who carried concomitant SET-binding Protein 1 (SETBP1) mutations, among other myeloid leukemia-associated mutations. The gene discussed is EZH2; the disease is myeloid leukemia.