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

A 71-year-old woman was admitted to our hospital because of a mediastinal mass. Chest computed tomography (CT) and fluorodeoxyglucose-positron emission tomography (FDG-PET) showed only 1 swollen mediastinal lymph node. Serum levels of carcinoembryonic antigen (CEA) were found to be elevated. Preoperative examination did not detect the primary lesion. A mediastinal lymphadenectomy was performed, and histologically, the tumor demonstrated poorly differentiated adenocarcinoma. Immunohistochemical staining for cytokine( CK) 7 and thyroid transcription factor( TTF) -1 were positive but were negative for CK20, suggesting a pulmonary origin. During 2-years postoperative follow-up, no signs of primary site growth can be detected. Surgical resection of mediastinal lymph node carcinoma of unknown primary site has the possibility of a good prognosis.