[Benign clear cell tumor of the lung; report of a case]

A 59-year-old woman was found to have an abnormal shadow on chest X-ray film during a general medical examination. A nodule with homogenous density and clear margin was seen in the lingular segment of the left lung. Since this shadow gradually enlarged during a 1.8 year follow up period, she was admitted to our hospital. A wedge resection was carried out by video-assisted thoracotomy. The resected tumor was histologically diagnosed as a benign clear cell tumor of the lung. Immunohistochemically, the tumor cells showed strong anti-melanoma monoclonal antibody (HMB-45) expression. This disease is extremely rare and only 31 cases including the present case have been reported in Japan.