[Mediastinal lymph node adenocarcinoma with unknown primary site; report of a case].

A 78-year-old man with old tuberculosis was pointed out the high CEA (347 ng/ml) and a mass shadow in right side of middle mediastinum. Examination by bronchoscopy showed no abnormal finding, cytological diagnosis of sputum was negative. In computed tomography (CT), there was tumor-like shadow in the right upper lobe and mass shadow in the right side of middle mediastinum, and we suspected of lung cancer. We performed a wedge resection in the right upper lobe with regional lymph node dissection. In the histological diagnosis, there were no malignant finding in the right lung, and mediastinal lymph nodes showed poorly differentiated adenocarcinoma. In immunohistochemistry staining, CEA was positive, surfactant apoprotein and thyroid transcription factor-1 (TTF 1) were negative. Postoperative course was uneventful and 50 Gy radiotherapy were given. CEA was decreased to 2.1 ng/ml 6 months after the operation. This case was highly suspected to be a rare case of T0N2M0 lung cancer.