The highest frequency of Tet2 mutation occurs in chronic myelomonocytic leukemia (CMML) (30–60%), followed by myelodysplastic syndrome (MDS) (20–35%) (Kosmider et al., 2009), acute myeloid leukemia (AML) (12–34%) (Grossmann et al., 2011), and lymphoid malignancies (2–33%) (Solary et al., 2014). The gene discussed is TET2; the disease is chronic myelomonocytic leukemia.