A 64-year-old male underwent bullectomy for right pneumothorax. During the operation, a bulla and pleural plaque were found, but there were no other abnormal findings. Seven months later, he presented with exertional dyspnea and imaging examinations revealed right pleural effusion and pleural nodules. Cytological examination of the pleural fluid showed isolated round to elliptic-shaped atypical cells with multiple eccentric nuclei. The diagnosis of malignant mesothelioma was established by histological examination combined with immunohistochemical analysis of pleural biopsy specimens. Early cytologic or histologic approaches should be considered in elderly patients with pneumothorax, especially those with a history of asbestos exposure and/or pleural plaque.
