[Mediastinal lymph node carcinoma without apparent primary lesion: report of case].

A 62-year-old man with dyspnea had an enlarged lymph node, 6.5 cm in size in the left hilum, but no primary carcinoma could be found. The patient underwent lymph node dissection under video-assisted thoracoscopic surgery, and the histological diagnosis was undifferentiated carcinoma. No primary lesion has been identified even in postoperative survey. The postoperative course was uneventful with no evidence of recurrence eight months after the operation.