What are the specifics of staging? How is the information put together to find a stage?
There are actually three different systems used to stage mesothelioma. One by the American Joint Committee on Cancer (AJCC) is used the most. It is a system similar to what is used to stage other cancers. It uses three parameters: T for Tumor, N for (lymph) nodes, and M for metastasis. This staging applies to pleural mesothelioma.
T groups indicate the size and local spread of the tumor.
T1: The tumor involves the right or left pleura lining the chest wall or diaphragm. It may or may not have spread to the lining of the lung (the visceral pleura).
T2: As above, but additionally, the mesothelioma has grown into a large area of the pleura lining the lung, the diaphragm, or actually into the lung.
T3: Similar to T2; however the tumor has now grown into the first layer of the chest wall, into the fat of the mediastinum (the space between the lungs), into the deep layers of the chest wall at a single place, or into the outer covering of the heart, the pericardium.
T4: The mesothelioma has grown similar to T2, but it has now grown into the deeper layers of the chest wall, which can include ribs or muscle. It may have grown through the diaphragm into the peritoneum. It can have grown into anything in the mediastinum, including the blood vessels, thymus, esophagus or trachea. The tumor could have grown into the spine, across to the pleura on the opposite side of the chest, through the heart lining or actually into the heart. Or it may have spread to the brachial plexus, which is a collection of nerves going to the arm.
N groups indicate the involvement of lymph nodes.
N0: No involvement of lymph glands.
N1: Tumor has spread to the nodes within the lung or around the area where the main bronchus enters the lung, on the same side as the tumor. These lymph nodes are called hilar lymph nodes.
N2: The tumor has spread to the space between the breastbone and the front of the heart or to the point at which the windpipe branches into left and right. Nodes with tumor are still on the same side as the mesothelioma.
N3: The tumor has spread to nodes near the collarbone on either side, and/or the hilar or mediastinal nodes on the opposite side from the main tumor.
M groups indicate metastasis, or spread of the tumor away from the primary site.
M0: Means no spread.
M1: The mesothelioma has spread to distant lymph nodes or other sites.
The T, N and M data are collected and combined to stage the tumor. Different patterns of T, N and M data are grouped into stages that have similar prognosis.
Stage I is T1, N0, M0.
Stage II is T2, N0, M0.
Stage III includes T1 or T2, N1 or N2, M0, and also T3, N0-2, M0.
Stage IV includes T4 with any N, M0. It also includes Any T, N3, and M0. Finally it includes any T or N with M1.
Also see: TNM