Background: Spontaneous pneumothorax is a relatively rare complication of lung cancer. Herein, we report two cases of lung cancer in situ with spontaneous pneumothorax as the initial symptom. Cases: Case 1: A 63-year-old male presented to our outpatient clinic with chest discomfort. He had a collapsed lung, and we inserted a chest drainage tube through the thoracic cavity to re-expand the lung. Computed tomography of the chest showed a large emphysematous bulla at the lung apex. Video-assisted thoracoscopic surgery was used to resect the bulla, and the final pathological diagnosis was an emphysematous bulla with adenocarcinoma in situ. Case 2: A 45-year-old man presented to our outpatient clinic with pain in the left chest and dyspnea. To treat an almost completely collapsed lung, we inserted a chest drainage tube into the thoracic cavity. Air leakage continued for a few days, so we resected the bulla. The final pathological diagnosis was an emphysematous bulla with a squamous cell carcinoma in situ. Conclusion: It is important to consider the possibility of lung cancer in patients with pneumothorax and emphysematous changes, especially in middle-aged or elderly patients.
