[Primary lung cancer presenting as spontaneous pneumothorax].

Pneumothorax is a rare manifestation of lung cancer. The mechanism by which pneumothorax occurs in lung cancer is not clear, and differing views have been expressed. Among 180 adults who presented with spontaneous pneumothorax from 1980 to 1992, eight had lung cancer: seven had squamous cell carcinoma and one had adenocarcinoma. All were men between 50 and 81 years old (average age, 66 years). In all patients, the pneumothorax occurred on the same side as the carcinoma. Thoracotomy was done in four patients. The results obtained by surgery indicated that pneumothorax may be caused by: 1) direct invasion of tumor into the pleura (patient 1); 2) rupture into the pleural space of dilated alveoli that are distal to the site of stenotic bronchial cancer (patient 7); 3) rupture into the pleural space of alveoli that had become distended to compensate for atelectasis due to obstructive bronchial cancer (patient 6); and 4) unknown (patient 2). These results suggest that lung cancer should always be considered as a possible cause of spontaneous pneumothorax in older patients.