JAK2 is a non-receptor tyrosine kinase that mediates signaling via the JAK-STAT pathway and the somatic, activating mutation V617F in the pseudokinase domain of JAK2 has been reported in over 90% of patients with polycythemia vera, 40-70% of essential thrombocytemia and 40-60% of primary myelofibrosis. JAK2 mutations have not been described in papillary thyroid carcinomas. Moreover, this variant has high prevalence in the East Asian population, and thus is predicted be a germline variant. Clinical correlation with other laboratory findings is recommended.