Essential Thrombocythemia

A 62-year-old woman was discovered to have a platelet count of 1,004,000 per cubic millimeter during evaluation for fatigue. Her medical history was notable only for hypertension and obesity (body-mass index [the weight in kilograms divided by the square of the height in meters], 34). She reported no symptoms other than fatigue, and all other blood counts were within normal limits. A review of previous laboratory reports obtained 8 and 3 years earlier revealed platelet counts of 290,000 and 595,000 per cubic millimeter, respectively. Analysis of peripheral blood was negative for JAK2 V617F but revealed an exon 9 mutation in the gene encoding calreticulin (CALR). How would you establish the diagnosis of essential thrombocythemia, and how would you manage this case?