TNM Staging System

The TNM Staging System has recently been developed by the American Joint Committee on Cancer (AJCC) and is very similar to staging systems used for most other cancers. The “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 for mesothelioma, information about the tumor, lymph nodes, and metastasis is combined in a process called stage grouping to assign a stage described by numbers from 1 to 4. Minor differences exist between the AJCC TNM staging system and the Butchart staging system.

• Stage 1: Mesothelioma involves the right or left pleura. It may also have spread into the lung, pericardium, or diaphragm on the same side. It has not yet spread to the lymph nodes.
• Stage 2: Mesothelioma has spread from the pleura on one side to the nearby peribronchial and/or hilar lymph nodes next to the lung on the same side. It may also have spread into the lung, pericardium, or diaphragm on the same side.
• Stage 3: Mesothelioma has spread into the chest wall muscle, ribs, heart, esophagus, or other organs in the chest on the same side as the primary tumor, with or without spread to subcarinal and/or mediastinal lymph nodes on the same side as the main tumor. Subcarinal nodes are located at the point where the windpipe branches to the left and right lungs. Mediastinal lymph nodes are located in the space behind the chest bone in front of the heart. Mesotheliomas with the same extent of local spread as in stage 2 that have also spread to subcarinal and/or mediastinal lymph nodes on the same side are also included in stage 3.
• Stage 4: Mesothelioma has spread into the lymph nodes in the chest on the side opposite that of the primary tumor, or directly extends to the pleura or lung on the opposite side, or directly extends into the peritoneum, or directly extends into organs in the abdominal cavity or neck. Any mesothelioma with evidence of distant metastases (spread to other organs through the bloodstream) or spread to organs beyond the chest or abdomen is included in this stage.