[Mediastinal lymph-node carcinoma with no apparent primary lesion; report of a case].

: A 57-year-old woman was admitted to our department because of a chest X-ray showing a mass shadow about 40 mm in diameter in the right side of the middle of the mediastinum. A chest computed tomography(CT) scan demonstrated a large tumor, adherent to the superior vena cava and right pulmonary artery. No other metastases and no primary tumor were found. The tumor was resected through median sternotomy. Intraoperative frozen section analysis showed that the mediastinal tumor was a metastatic lymph-node carcinoma. Postoperative examination, too, did not detect the primary lesion. Radiotherapy was given after the operation. This case was thought to be a very rare case of T0N2M0 lung cancer or primary mediastinal lymph-node carcinoma (yolk sac tumor).