Extreme thrombocytosis in low-risk essential thrombocythemia: Retrospective review of vascular events and treatment strategies

Formal diagnosis of essential thrombocythemia (ET) requires a plateletcount of≥450×109/L that is associated with morphologic or molec-ular evidence of an underlying myeloproliferative neoplasm (MPN)that is not otherwise classified as polycythemia vera (PV), prefibroticor overt primary myelofibrosis (PMF).1Approximately 22% of patientswith ET present with a platelet count of≥1000×109/L, which is arbi-trarily referred to as extreme thrombocytosis (ExT).2,3The particularpresentation is quite unnerving for both patients and their physiciansbecause of assumed increased risk for thrombotic complications. Inthis regard, despite the lack of supporting evidence, some physiciansare inclined to institute cytoreductive therapy in the presence of ExT,in otherwise low-risk ET (defined by the absence of thrombosis historyand age≤60 years).