[Subcutaneous myeloid sarcoma in a patient with essential thrombocythemia that transformed into acute myeloid leukemia].

Since November 2008, an 80-year-old man had been administered hydroxyurea and aspirin for the treatment of essential thrombocythemia (ET). In January 2012, his white blood cell count was markedly elevated, and he was treated with busulfan and cytarabine. In October 2012, he was hospitalized because of fever and general malaise, and a central venous port was placed in the right anterior chest owing to difficulty obtaining peripheral vascular access. Approximately 2 weeks after port placement, a subcutaneous mass was observed near the port. The patient died in November 2012 owing to exacerbation of the original disease. Autopsy revealed transformation to acute myeloid leukemia( AML; M2 subtype) and myeloid sarcoma (MS) in lymph nodes and the right anterior chest. The incidence of transformation of ET to AML is low, and MS as a comorbidity is rare. However, the risk of MS complications should be considered in patients with hematological malignancies due to recent increases in the use of central venous ports in such cases.