JAK2 and essential thrombocythemia: In the UKB, of the 26 individuals with JAK2 V617F and concurrent autosomal mCAs who developed incident hematologic cancers, there were 10 cases of polycythemia vera, 4 cases of myeloproliferative neoplasm NOS, 4 cases of myelofibrosis, 3 cases of essential thrombocythemia, 2 cases of AML, and 1 case of each of the following: APML, CML, and MDS.