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

We experienced a rare case of a 38-year-old man with mediastinal lymph node carcinoma of unknown primary site. He had an abnormal shadow of upper mediastinal mass in a health check, and he was referred to our hospital. Chest computed tomography( CT) showed only one swollen mediastinal lymph node, and positron emission tomography(PET) revealed an accumulation of fluorodeoxyglucose in the nodule. Serum levels of neuron specific enolase (NSE) were found to be elevated. Preoperative examination did not detect the primary lesion. She underwent a mediastinal lymphadenectomy. The pathological diagnosis of the lesion was large cell neuroendocrine carcinoma. He was given platinum-based combined chemotherapy and radiotherapy as adjuvant therapy. He has been well without any sign of recurrence for 1 year after surgery. Surgical resection of mediastinal lymph node carcinoma of unknown primary site has the possibility of a good prognosis.