Stage I includes: (T1, N0, M0); IA: (T1a, N0, M0); IB: (T1b, N0, M0). T1: Pleural mesothelioma with a tumor limited to the ipsilateral parietal pleura with or without mediastinal pleura and with or without diaphragmatic pleural involvement. T1a: Pleural mesothelioma with no involvement of the visceral pleura. T1b: Pleural mesothelioma with a tumor also involving the visceral pleura N0: No regional lymph metastasis. M0: No distant metastasis. (AJCC 7th ed.) [from NCI]