Pleural mesothelioma is the only form of mesothelioma that has been successfully staged as it is the commonest type of the disease.There are three different staging systems used to determine the extent of pleural mesothelioma, each one of these three different staging systems measure different aspects of the cancer,including the size of the tumor, the level of spreading{metastases}and the probable involvement of lymph nodes.

The stage of mesothelioma at the time of diagnosis determines to a very large extent the type of treatment prescribed by the doctor.

Butchart System

The Butchart System is the oldest staging system for malignant mesothelioma and is the one most commonly used by doctors and specialists to diagnose and treat the tumor. The Butchart System is based on the tumor size (mass) and divides malignant mesothelioma into four stages:

• Stage 1 - Malignant mesothelioma has affected the right or left side of the chest cavity (pleural lining) and may be seen in the diaphragm.

• Stage 2 - Malignant mesothelioma has been found in the pleura on both sides of the body and may have also moved into the heart, stomach, or esophagus on both sides. Lymph nodes may be affected.

• Stage 3 - Malignant mesothelioma has reached the abdominal cavity (peritoneum). Lymph nodes past the chest may be affected.

• Stage 4 - Malignant mesothelioma has reached other organs and has entered the blood stream.

TNM System

The TNM System is a more modern staging system for malignant mesothelioma. The TNM System is based on the extent of the tumor, metastasis, and lymph node involvement. Again, the TNM System divides malignant mesothelioma into four stages:

• Stage 1 - Malignant mesothelioma is present in the left or right chest cavity (pleura) and may have metastasized to the lung, the sac around the heart (pericardium) or the diaphragm on the same side. Lymph nodes at stage 1 are not involved.

• Stage 2 - Malignant mesothelioma has reached from one side of the chest cavity to a lymph node near the lung area on the same side as the cancer. The cancer has metastasized to the diaphragm, pericardium (sac around the heart), or the lung on the same side as the primary tumor.

• Stage 3 - Malignant mesothelioma has penetrated the chest lining, heart, esophagus, muscle, ribs and vital organs within the chest cavity on the same side as the cancer. Lymph nodes may or may not be involved during this stage.

• Stage 4 - Malignant mesothelioma has metastasized to the pleural area and the lymph nodes on the opposite side of where the cancerous tumor is located. It may also have reached the chest cavities or lungs on both sides, or may have spread to the abdomen.

Brigham System

The Brigham System is the most modern of the three malignant mesothelioma staging systems. The Brigham System looks at different variables such as the involvement of the lymph nodes and the surgical ability to remove a malignant mesothelioma tumor (resectability). For this reason, it is not used very often to stage mesothelioma, as the cancer is rarely operable. The Brigham System divides malignant mesothelioma into four stages:

• Stage 1 - Malignant mesothelioma tumor is still resectable (able to be removed surgically) and the lymph nodes are not affected.

• Stage 2 - Malignant mesothelioma tumor is still resectable, but the lymph nodes are now affected.

• Stage 3 - Malignant mesothelioma tumor is not resectable and the malignant mesothelioma has penetrated the heart, chest wall, abdominal cavity or diaphragm. Lymph nodes may or may not be affected.

• Stage 4 - Malignant mesothelioma tumor is not resectable and has completely metastasized (spread throughout the body).

Process of Staging Malignant Mesothelioma

When mesothelioma is diagnosed by a physician or specialist, they must determine the extent of the cancer and how far it has spread. Most often, they will use imaging procedures to see inside the chest or abdomen to help determine the staging of the malignant mesothelioma. The imaging options physicians may use include:

• Chest X-ray

• CT scan of the chest and/or abdomen

• MRI scan of the chest and/or abdomen

• PET of the chest and/or abdomen