Inactivating somatic mutations in TET2, a gene regulating DNA demethylation, are common in both myeloid and lymphoid malignancies including chronic myelomonocytic leukemia, acute myeloid leukemia (AML), myelodysplastic syndrome, angioimmunoblastic T cell lymphoma and, at a lower frequency, diffuse large B cell lymphoma and mantle cell lymphoma [2]. The gene discussed is TET2; the disease is acute myeloid leukemia.