ABL1 and essential thrombocythemia: According to WHO 2016 classification, BCR-ABL negative MPNs are classified into different nosological categories as polycythemia vera (PV), essential thrombocythemia (ET), primary myelofibrosis (PMF, overt fibrotic and prefibrotic stage), and other rare disorders as chronic neutrophilic leukemia (CNL), chronic eosinophilic leukemia, not otherwise specified (CEL, NOS) and unclassifiable MPN (MPN-u) [2,3].