術前化学療法後にFDG異常集積を認めた縦隔原発非セミノーマ性巨大胚細胞性腫瘍の一切除例(Successful Resection of a Giant Mediastinal Non- Seminomatous Germ Cell Tumor Showing Fluorodeoxyglucose Accumulation after Neoadjuvant Chemotherapy: Report of a Case)