[Hematological neoplasia associated with primary mediastinal germ-cell tumor treated with hematopoietic stem cell transplantation].

The occurrence of a primary mediastinal germ cell tumor and hematological neoplasia provides a poor prognosis that is known to be fatal at a median of 6 months after onset. We report the case of a 15-year-old male who was treated with chemotherapy and hematopoietic cell transplantation based on a report of a surviving case. At diagnosis, the patient had an unresectable mediastinal tumor with elevated alpha-fetoprotein and human chorionic gonadotropin levels and acute megakaryoblastic leukemia. We prioritized treatment with chemotherapy for the tumor owing to the oncological emergency. We then performed leukemia induction therapy and achieved complete remission. Although we used CDDP in combination with intensive therapy, the mediastinal tumor grew too large for it to be safely resected. We transplanted bone marrow from the patient's human leukocyte antigen-haploidentical sibling upon conditioning with busulfan-melphalan. After 44 days, the leukemia recurred in the patient's central nervous system. This was followed by various post-transplant complications, and the patient died of organ failure that was associated with infectious diseases. At necropsy, a poorly engrafted bone marrow was observed. The mediastinal tumor was primarily necrotic, although some immature teratoma components were observed. No leukemic precursor cells were detected. Residual mediastinal tumors may be associated with the recurrence of leukemias. We seek a treatment strategy that enables early tumor resection and high-dose chemotherapy. Further case studies are warranted along with the development of effective treatment methods.