In the TNM system, T stands for tumor, N for lymph nodes and M for metastases, or spread of the tumor to other organs. There are multiple different permutations, from T values of 1 to 4, N values of 1 to 3 and M values of 0 and 1. These 3 factors are put together to make a slightly different, four-level staging system in the TNM system.
- Stage 1. Stage 1 is T1, N0, M0, meaning the mesothelioma is in either the right or left pleura involving the chest wall or diaphragm. There may be a tiny spot on the visceral pleura, which covers the lung, but it has spread nowhere else.
- Stage 2. Stage 2 is T2, N0, M0, which is like Stage 1 except that the tumor has grown into the diaphragm, or there is a lot of tumor in the pleura around the lung, or it is in the lung itself. It still has not spread anywhere else.
- Stage 3. Stage 3 includes T1 and T2, N1 or N2, and M0. In this case the tumor can be as it is in Stage 1 or Stage 2. It may have spread to the lymph nodes but only in the chest on the same side as the tumor. Stage 3 can also include T2, N0 to N2, and M0. In these cases the mesothelioma has spread into the first layer of the chest wall, the fatty area of the mediastinum in the middle of the chest, a single spot in the chest wall, or the pericardium covering the heart. In addition, it may have spread to lymph nodes in the chest on the same side, but not farther.
- Stage 4. Stage 4 can include T4 with any N and M0. In this case, the mesothelioma has spread through the chest wall, through the diaphragm into the abdomen, through any of the organs in the chest, the spine, to the pleura on the other side, through the heart lining even all the way into the heart. It may or may not be in lymph nodes, but it has not spread farther in the body. Or with any T, N3 and M0, the tumor can be of any size, but it has spread to lymph nodes near the collarbone, on either side, and/or to lymph nodes in the middle of the chest opposite the tumor. It has not metastasized. Finally, the stage of any T and N with M1 includes a tumor of any size with or without lymph node spread, but which has spread to distant sites in the body.
The TNM system was developed by the American Joint Committee on Cancer, and it is the most commonly used staging system. In this system, Stage 1 is considered early. All other stages are considered advanced.
Dr. Kaplan
