Aims of our study were (1) to investigate the presence of TET2 mutations in MPN patients with or without the JAK2 V617F mutation and (2) to establish a possible relationship between clinical and laboratory findings in the context of polycythemia vera (PV), essential thrombocytemia (ET), primary myelophibrosis (PMF) and myeloproliferative neoplasms unclassifiable (MPNs-U). The gene discussed is TET2; the disease is acquired polycythemia vera.