CMML is the most frequent and is characterized by the presence of sustained peripheral blood monocytosis with recurrent mutations involving TET2, SRSF2, and ASXL1; with RAS pathway mutations and JAK2V617F being relatively enriched in proliferative CMML subtypes (WBC ≥ 13 × 109/L). This evidence concerns the gene TET2 and chronic myelomonocytic leukemia.