[A case of unknown origin cancer of the mediastinal lymph node].

We encountered an unusual case with a sole cancer focus at the mediastinal lymph node. The patient was a 44-year-old man who visited our department with a chief complaint of chest pain. Subsequent chest X-ray and CT revealed an enlargement of a mediastinal lymph node. The excised lymph node measured 6.8 x 5.5 x 4.0 cm and weighed 51 g. It showed metastasis of poorly differentiated adenocarcinoma. In spite of a thorough systemic examination, no primary foci were detected. Lymph node tumors of the mediastinum or hilar region with unknown primary foci are extremely rare (there have been only 2 reported cases of lesions found at the hilar lymph node with unknown primary focus). There have been no reports on cancerous foci limited to the mediastinal lymph nodes. The patient has been under chemotherapy and radiotherapy during the past 3 years following surgery. He shows no signs of recurrence. It is a very unusual case. A possible classification of T0N2M0 has been considered.