Butchart Staging System

Stage I: Mesothelioma is present within the right or left pleura, and may also involve the lung, pericardium, or diaphragm (the muscle separating the chest from the abdomen) on the same side.
Stage II: Mesothelioma invades the chest wall or involves the esophagus (food passage connecting the throat to the stomach), heart, or pleura on both sides. The lymph nodes in the chest may also be involved.
Stage III: Mesothelioma has penetrated through the diaphragm into the peritoneum (lining of the abdominal cavity). Lymph nodes beyond those in the chest may also be involved.
Stage IV: There is evidence of distant metastases (spread through the bloodstream to other organs).
Another staging system has recently been developed by the American Joint Committee on Cancer (AJCC). This is a TNM system, similar to staging systems used for most other cancers. T stands for tumor (its size and how far it has spread to nearby organs), N stands for spread to lymph nodes and M is for metastasis (spread to distant organs). In TNM staging, information about the tumor, lymph nodes, and metastasis is combined in a process called stage grouping to assign a stage described by Roman numerals from I to IV. Minor differences exist between the AJCC TNM staging system and the Butchart staging system.