Megakaryoblastic transformation of chronic myelomonocytic leukemia presenting with severe bone pain

A 77-year-old woman, who had suffered from osteoporosis with compression fractures of vertebrae, was admitted to our hospital because of increasing bone pain. She had anemia and monocytosis, and was diagnosed as chronic myelomonocytic leukemia (CMML). Although chemotherapy was initiated, she died from pneumonia. Autopsy revealed multiple tumors composed of megakaryoblastic cells in her bone marrow and extramedullary organs and, therefore, the pathological diagnosis was made as megakaryoblastic transformation of CMML. Severe bone pain was considered to be a symptom of megakaryoblastic transformation of CMML.