A Case of Mediastinal Lymph Node Carcinoma of Unknown Primary Site.

: A 63-year-old man was pointed out with a mediastinal tumor on chest computed tomography (CT). On positron emission tomography-CT, fluorodeoxyglucose accumulation with a maximum standardized uptake value of 12.70 was seen in this tumor. Scar-like nodule was found in the apex of the right lung, but no abnormal accumulation was observed in this nodule. The level of carcinoembryonic antigen was abnormally elevated. We performed mediastinal tumorectomy under thoracoscopic surgery. Since arterial oxygen saturation fell during intraoperative one-lung ventilation, we finished the surgery without resection of right apex nodule. Histologically, mediastinal tumor was diagnosed as metastatic adenocarcinoma in lymph node. Because immunohistochemical staining suggested lung adenocarcinoma as the primary site, the right apex nodule was resected. Pathological diagnosis of this nodule was scar fibrosis. No other malignant lesions were detected, and therefore we finally diagnosed this tumor as mediastinal lymph node carcinoma of unknown primary site. The patient was given adjuvant chemotherapy, and at present, 37 months after surgery, the patient remains free of the disease.