For instance, detecting BCR-ABL1 transcript, the causative agent of rare chronic myeloid leukemia mimicking essential thrombocytemia (ET), and JAK2, CALR, MPL mutations, which are present in three myeloproliferative neoplasms: ET, primary myelofibrosis, and polycythemia vera [101,102,103]. The gene discussed is JAK2; the disease is essential thrombocythemia.