This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Myeloproliferative Disorders, Subject name: Pathology
[{'content': 'Which of the following is not a myeloproliferative neoplasm? \nSelect and explain. \nA. Polycythemia vera, B. Juvenile myelomonocytic leukemia, C. Chronic myeloid leukemia, D. Essential thrombocythemia', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Juvenile myelomonocytic leukemia is not included in the category of MPNs (myeloproliferative neoplasms) in WHO classification Examples of myeloproliferative neoplasms: Chronic myeloid leukemia Polycythemia vera Primary myelofibrosis Essential thrombocythemia Chronic eosinophilic leukemia Activating JAK2 mutations are seen in: Nearly all cases of polycythemia vera Approx. 50% of cases of primary myelofibrosis and essential thrombocythemia BCR-ABL1 translocation seen in CML', 'role': 'assistant'}]