The gene encoding the DNA demethylating enzyme TET2 is mutated in 10–20% of AML cases, resulting in an unfavourable disease outcome [57,58,59], as well as 10–20% of MDS/MPN patients [60,61], 40–50% of patients with CMML [59,62], and about 10% of DLBCL patients [63]. The gene discussed is TET2; the disease is acute myeloid leukemia.