[Mediastinal Growing Teratoma Syndrome during Chemotherapy, Presenting as a Huge and Inoperable Tumor].

A 22-year-old male was diagnosed with a metastatic nonseminomatous germ cell tumor in the mediastinum with an elevated serum alpha-fetoprotein(AFP)concentration. Histopathological findings following percutaneous biopsy revealed the presence of a mature teratoma. Bleomycin, etoposide, and cisplatin(BEP)chemotherapy resulted decreased his serum AFP. However, the tumor became enlarged and was deemed inoperable due to size. Radiographic examination indicated diffuse calcification of the tumor mass. Growing teratoma syndrome in a patient with a primary mediastinal nonseminomatous germ cell tumor is extremely rare.