Molecular criteria take a preponderant place because besides the three well-known driver mutations, it is more and more necessary to search clonality markers as ASXL1, DNMT3A, EZH2, TET2, IDH1/2, SRSF2 and SF3B1 because they are more frequent in PMF and in advanced MPN. The gene discussed is IDH1; the disease is myeloproliferative neoplasm.