TET2 mutations are common in haematological neoplasms and can occur in 30% of myelodysplastic syndrome (MDS), 20% of myeloproliferative neoplasms (MPNs), 30% of secondary acute myeloid leukemia (sAML), 17% of novel AML, and 50–60% of chronic myelomonocytic leukemia (CMML) cases [16–19]. This evidence concerns the gene TET2 and chronic myelomonocytic leukemia.