Secondary spontaneous pneumothorax as an initial manifestation of lung cancer: a case report.

Background: Secondary spontaneous pneumothorax (SSP) is a rare but critical initial clinical manifestation of lung cancer, often masquerading as benign bullous disease. The diagnostic challenge is significantly amplified when the underlying malignancy is occult on initial imaging and impalpable during surgical exploration. This report describes a rare case of early-stage adenocarcinoma presenting as SSP in the context of diffuse pulmonary bullae, highlighting the risk of underdiagnosis in high-risk populations. Case Description: A 55-year-old male with a 60 pack-year smoking history presented with acute-onset right-sided chest pain. Initial high-resolution computed tomography (HRCT) confirmed a right-sided pneumothorax associated with multiple bilateral bullae and localized emphysema; however, no discrete nodules or masses were identified. The patient underwent video-assisted thoracoscopic surgery (VATS) for apical bullae resection and pleurodesis. Intraoperative exploration revealed multiple bullae but no palpable solid lesions. Surprisingly, postoperative histopathological examination identified an infiltrating, moderately differentiated lung adenocarcinoma (6mm in diameter) characterized by 80% acinar and 20% lepidic growth patterns. Immunohistochemical staining was positive for CK7, Napsin A, and TTF-1. Although the patient declined further staging or radical resection, he has remained recurrence-free during 16 months of postoperative follow-up. Conclusion: Spontaneous pneumothorax in high-risk elderly smokers may mask occult lung cancer, even with negative HRCT findings. Clinicians should maintain high suspicion and routinely utilize intraoperative frozen section analysis for resected bullae to prevent delayed diagnosis and ensure timely oncological management.