T1    T1a   Tumor limited to the ipsilateral parietal pleura, including mediastinal and diaphragramatic pleura                            No involvement of the visceral pleura         T1b   Tumor involving the ipsilateral parietal pleura, including mediastinal and diaphragramatic pleura                            Scattered foci of tumor also involve in the visceral pleura T2             Tumor involving each of the ipsilateral pleura surfaces (parietal, mediastinal and diaphragramatic                             and visceral pleura) with at least one of the following features:          ✓      Involvement of diaphragmatic muscle          ✓      Confluent visceral pleural tumor (including the fissures) or extensions of tumor from visceral pleura into the underlying pulmonary parenchyma          T3     Describes locally advanced but potentially resectable tumor                          Tumor involving all of the ipsilateral pleura surfaces (parietal, mediastinal and diaphragramatic                          and visceral pleura) with at least one of the following features:          ✓     Involvement of the endotharacic facia          ✓     Extension into the mediastinal fat          ✓     Solitary, completely resectable focus of tumor extending into the soft tissues of the chest wall          ✓     Nontransmural involvement of the pericardium           T4      Describes locally advanced technically unresectable tumor Tumor involving all of the ipsilateral pleura surfaces (parietal, mediastinal and diaphragramatic                          and   visceral pleura) with at least one of the following features:          ✓     Diffuse extension or multifocal masses of tumor in the chest wall, with or without associated rib destruction          ✓     Diffuse transdiaphragramatic extension of tumor to the peritoneum          ✓     Direct extension of tumor to the contralateral pleura          ✓     Direct extension of tumor to one or more mediastinal organs          ✓     Direct extension of tumor into the spine          ✓    Tumor extending through to the internal surface of pericardium, with or without a pericardial effusion; or tumor involving the  myocardium N-lymph nodes        Nx      Regional lymph nodes cannot be assessed        N0      No regional lymph node metastases        N1      Metastases in the ipsilateral bronchopulmonary or hilar lymph nodes        N2      Metastases in the subcarinal or theipsilateral mediastinal lymph nodes, including the ipsilaternal mammary nodes        N3      Metastases in the contralateral mediastinal, contralateral internal mammary, contralateral supraclavicular lymph nodes                  M-      metastases         Mx      Presence of distant metastasis cannot assessed        M0      No distant metastasis        M1      Distant metastasis present Stage Description Ia T1xN0M0 Ib T1bN0M0 II T2N0M0 III AnyT3M0 AnyN1M0 AnyN2M0 IV AnyT4 AnyN3 AnyM1

Table 1: The International Mesothelioma Interest Group (IMIG) staging system.