JAK2-negative acute monocytic leukemia with TET2 mutation in essential thrombocythemia with JAK2 mutation with literature review

Essential thrombocythemia (ET) is an indolent myeloproliferative neoplasm (MPN) with a transformation to acute myeloid leukemia in <5% of patients. A 79-year-old man with JAK2V617F-positive ET exhibited leukocytosis with an increase in monoblastic cells, leading to a diagnosis of acute monoblastic and monocytic leukemia. Leukemic cells carried a TET2 mutation but not JAK2V617F mutation. We concluded that the TET2 mutation occurred in MPN-initiating cells and overcame JAK2-mutated cells. The absence of a JAK2 mutation in the leukemic cells in this case suggests the leukemia emerged from a JAK2-negative MPN cell clone carrying the TET2 mutation.