Mesothelioma Staging

Treatment and outlook for a patient with mesothelioma depends a great deal upon the stage (extent) of the patient's cancer.

Three staging systems exist for mesothelioma, but the American Cancer Society, the American Joint Committee on Cancer, and the International Mesothelioma Interest Group have endorsed the TNM System, which considers variables of tumor mass and spread, as well as lymph node involvement and metastasis. The Butchart System and the Brigham System, on the other hand, narrowly focus on tumor mass and the ability to surgically remove the mesothelioma tumor.

The TNM Staging System

The TNM Staging System is similar to those used for most other cancers. TNM is an acronym, where T stands for the size of a tumor, N stands for spread to the lymph nodes, and M refers to metastasis- whether the cancer has spread to distant organs. Each of the three categories involves four stages, which are then grouped together to determine an overall stage for a case of mesothelioma (stage grouping).

Stage 1 mesothelioma involves localized cancer in either the left or right pleura lining the chest. If the cancer has spread, at this stage it may only have reached a few small areas of the outer lining of the lung. Mesothelioma may not be found in the lymph nodes or other areas of the pleural or peritoneal cavities at this stage.

If the patient's pleural mesothelioma has spread from the pleural lining of the chest into the outer lining of the lungs, the diaphragm or the lungs, the cancer will be categorized as Stage II mesothelioma. However, at this stage, the cancer still has not spread to the lymph nodes or distant sites.

Once pleural mesothelioma has reached the lymph nodes of the chest on the same side as the pleural tumor, it will be considered Stage III mesothelioma. Mesothelioma will also be categorized as Stage III if the pleural mesothelioma has spread into the first layer of the chest wall or a single place within the chest wall, the fatty part of the mediastinum (the area between the pleural cavity, containing the esophagus, trachea, and thymus), or the outer layer of the heart.

Pleural mesothelioma reaches Stage IV when the cancer has spread into the chest wall and muscle or ribs, through the diaphragm, into any organ of the mediastinum, into the spine, across the pleura to the opposite side of the chest from the point of origin, through the heart lining or into the heart, or into the nerves leading to the arm (brachial plexus). The cancer, at this stage, might not have reached the lymph nodes and has not spread to distant areas of the body. Pleural mesothelioma may also be diagnosed as Stage IV if it has spread to distant sites of the body, or if it has not spread to distant sites but has spread to the lymph nodes of the collar bone, or to the hilar (the depression in the surface of a lung that forms the opening through which the bronchus, blood vessels, and nerves pass) or mediastinal lymph nodes on the opposite side of lung from where the cancer originated.

The Butchart Staging System

The oldest staging system for mesothelioma is the Butchart System, which is based on differentiations in the mass of mesothelial tumors. As with the TNM Staging System, mesothelioma is categorized into four stages.

Under the Butchart System, if a mesothelial tumor is found in the right or left pleura, and possibly in the diaphragm on the same side as the affected pleura, the cancer is considered Stage I mesothelioma. Stage II mesothelioma occurs if the tumor invades the chest wall, if it implicates the esophagus, heart or both sides of the pleura, or has reached the lymph nodes of the chest. If the mesothelioma has penetrated the diaphragm and made its way into the lining of abdominal cavity, it will be labeled Stage III mesothelioma, even if the cancer has not reached the lymph nodes. Under this system, Stage IV mesothelioma is reserved for cases where the cancer has metastasized to organs other than those mentioned.

The Bringham Staging System

The Bringham Staging System is the most recent system devised for categorizing cases of mesothelioma. It focuses on whether the patient's mesothelial tumor can be surgically removed, and it too involves four distinct stages of the disease.

If a patient's mesothelioma has not spread to the lymph nodes and the tumor can be removed with surgery, the cancer will be labeled Stage I mesothelioma. If the cancer has spread to the lymph nodes, but the tumor is operable, the mesothelioma is considered Stage II under this system. With or without having spread to the lymph nodes, a patient is considered to have Stage III mesothelioma if the cancer has penetrated the chest wall, heart, diaphragm or abdominal cavity and the tumor cannot be removed with surgery. If the cancer has metastasized, under the Brigham System, the patient is said to have Stage IV mesothelioma.