[Lung Cancer Incidentally Detected by a Subcutaneous Nodule at the Drainage Site for Pneumothorax].

A 43-year-old male patient underwent thoracic drainage for the treatment of right pneumothorax. After 6 months, the patient visited our department because of a subcutaneous nodule found at the drainage site. Chest computed tomography revealed a mass lesion associated with a cavity in the right upper lobe of the lung and a subcutaneous nodule. Surgical resection was performed and both the pulmonary lesion and subcutaneous nodule were found to be adenocarcinoma. Although immunohistochemical analysis suggested that the pulmonary lesion was primary lung cancer, there were neither intrathoracic exposure of the tumor nor tumor cells in the pleural lavage cytology. The expression pattern of subcutaneous tumor in the right chest was slightly different from that of the lung lesion by immunohistochemistry. Therefore, it was difficult to determine whether this subcutaneous nodule was a tumor implantation through the drainage procedure or subcutaneous metastasis from the primary tumor.