The IMIG system
The IMIG is based on the TNM staging system.
The TNM system of staging is most commonly used system in cancer staging. The TNM system describes the extent of the primary tumor (T), the involvement of nearby lymph nodes (N), and the absence or presence of distant metastases (M).
Once the TNM categories have been decided, this information is grouped together to give the stages. Stage 1 is the initial or the earliest stage and stage 4 is the most advanced or late stage of the cancer.
TNM system includes the following four tumor stages:
T1: In this stage the pleura of the right or left lung (chest lining) is affected by the mesothelioma. The mesothelioma has advanced to the lining surrounding the lung and possibly to a few added minute spots.
T2: In this stage the mesothelioma tumor has involved one side of the chest, but it has extended into the lung’s outer lining, or the diaphragm, or the lung’s interior.
T3: In this stage mesothelioma has completely involved one side of the chest, but it has also spread into the chest wall’s first layer, or a one place in the chest wall, or the heart’s outer covering layer (pericardium) , or the mediastinum’s fatty part (the mediastinum is the area containing the trachea, esophagus and thymus).
T4: It is the most developed or advanced tumor stage. Mesothelioma in this stage has spread from either the right or left pleura lining into the chest wall, ribs, muscles, or it has spread to the trachea, blood vessels, esophagus, or thymus. It may spread (metastasize) to the spine as well. The cancer can also involve the opposite side of the chest and can spread through the heart lining (pericardium) and may be affecting the heart tissue itself. The cancer can also spread to the brachial plexus of nerve system, which is the system of nerves n armpit that controls the arm.
Lymph Node Stages
Lymph nodes are bean shaped aggregates of special immune systems cells located under the armpits, in the groin, abdomen, neck and elsewhere in the body. Malignant cancers commonly involve the adjacent lymph nodes. There are three N stages in the TNM system to describe how far the mesothelioma has spread to the lymph nodes.
N0: This shows that the cancer has not involved any lymph nodes.
N1: In this stage cancer cells have spread to lymph nodes on the same side of the chest of diaphragm.
N2: In this stage the cancer affects lymph nodes that are located on the side of the mesothelioma’s origin. So in this stage the mesothelioma has involved the lymph nodes in front of the heart (the space called the mediastinum) or the lymph nodes near the left or right bronchi.
N3: This stage shows that the cancer has spread to lymph nodes near the clavicle (or collarbone) and/or to lymph nodes on the contrary side of the mesothelioma affected lung.
Metastasis Stages
Metastasis stages show the extend of tumor spread to the other parts of the body which are not in direct relationship to the cancer.
Stage I (T1, N0, M0): At this stage, mesothelioma has involved the lymph nodes or to distant organs. It has only involved the one side of the pleural lining and perhaps has spread in a few spots to the lung’s outer lining.
Stage II (T2, N0, M0): In this stage mesothelioma has spread into the lung’s outer lining or into the diaphragm or inside the lung. No lymph node involvement and the mesothelioma has not spread to distant organs.
Stage III (T1 or T2, N1 or N2, M0; or T3, N0 or N1 or N2, M0): The mesothelioma in this stage has not metastasized to distant organs, but it has spread significantly in the chest cavity. It may involve the lung’s inner, the heart’s outer layer, and/or the diaphragm. It may or may not engage the lymph nodes.
Stage IV (T4, any N, M; or any T, N3, MO; or any T, any N, M 1): In this stage the tumor is so advanced that it has spread to the opposite side of the chest cavity; the cancer may be inside the lungs, the heart, and/or may be in the mediastinum (the area containing the trachea, blood vessels, esophagus, and thymus). It may have reach to the spine and/or the brachial plexus .Once pleural mesothelioma is this advanced, it called as stage IV.