Malignant pleural mesothelioma presenting as a spontaneous pneumothorax

Malignant pleural mesothelioma (MPM) is thought to arise from the mesothelial cells that line the pleural cavities. Most patients initially experience the insidious onset of chest pain or shortness of breath and have a history of asbestos exposure. MPM rarely presents as spontaneous pneumothorax. We report two male patients who presented with a spontaneous hydropneumothorax. One was exposed to asbestos and the other was not. Computed tomography showed tiny nodules with pleural thickness. They both underwent pleural effusion cytology and/or pleural biopsy. Therefore, the pathological diagnosis of MPM was obtained in both cases. We also reviewed 16 Japanese MPM cases with pneumothorax including our two patients. More than half of the patients suffered from pneumothorax repeatedly. We emphasize the need to obtain a pathological diagnosis of pleural effusion cytology and/or pleural biopsy in older patients presenting with a spontaneous hydropneumothorax.