Stages of Mesothelioma

Stages of mesothelioma, or TNM staging, is a way to assign a level to a patient’s mesothelioma based on the certain characteristics. Those characteristics include the tumor’s size and how far it has spread to organs and lymph nodes. This information is quantified by assigning a stage to each: a tumor stage, a lymph node stage and a metastasis stage. This information is them combined in a process called stage grouping to assign a single TNM stage for the cancer described by Roman numerals from I to IV. The TNM system is similar to staging systems used for most other cancers. TNM staging was developed by the International Mesothelioma Interest Group and adopted by the American Joint Committee on Cancer.

Here’s how it works: Doctors will assign letters T, N or M and a corresponding Roman numeral based on the characteristics described above. Patients with lower stage numbers have a better prognosis and a broader range of potential mesothelioma treatment options.

Tumor Stages

Information about the tumor is defined by assigning a number from 1 to 4 to signal the degree that the main tumor has spread in and around the pleura. The higher the T stage, the further the original tumor mass has spread to nearby structures like the chest wall, lung tissue or other areas in the chest.

T1

Mesothelioma involves either the right or left pleura lining the chest. It has only spread to the pleura covering the lung, with the exception of possibly a few other small spots.

T2

Mesothelioma involves either the right or left pleura lining the chest and has spread from the lining of the chest into 1) the outer lining of the lung, 2) the diaphragm, or 3) into the lung itself.

T3

Mesothelioma involves either the right or left pleura lining the chest and has spread into 1) the first layer of the chest wall, 2) the fatty part of the mediastinum, 3) a single place in the chest wall, or 4) the outer covering layer of the heart.

T4

Mesothelioma involves either the right or left pleura lining the chest and has spread 1) into the chest wall, either muscle or ribs, 2) through the diaphragm, 3) into any organ contained in the mediastinum (esophagus, trachea, thymus, blood vessels), 4) into the spine, 5) across to the pleura on the other side of the chest, 6) through the heart lining or into the heart itself, or 7) into the brachial plexus (nerves leading to the arm).

Node Stages

The node stage identifies the degree to which the cancer has spread to the lymph nodes. N stages range from 0 to 3, so that 0 means that mesothelioma cells have not spread to the lymph nodes at all, and larger numbers signal spread to more distant lymph nodes in the chest area.

N0

No spread to lymph nodes.

N1

Spread to lymph nodes on the same side of the chest as the mesothelioma.

N2

Spread to lymph nodes around the point where the windpipe branches into the left and right bronchi or to lymph nodes in the space behind the chest bone and in front of the heart (mediastinum). Affected lymph nodes are on the same side of the cancerous lung.

N3

Spread to lymph nodes near the collarbone on either side, to hilar or mediastinal lymph nodes on the side opposite the cancerous lung.

Metastasis Stages

The level of metastasis, or spread to other organs in the body, is communicated through the M stage. There are only two M stages to signal that mesothelioma cells have or have not spread to distant organs in the body.

M0

No spread to distant organs or areas.

M1

The cancer has spread distantly.

TNM Stages (I, II, III or IV)

The separate T, N and M stages are combined under the TNM staging system to provide a single stage designation that expressly considers the tumor size and spread, lymph node involvement and metastasis to other organs of the body. The system is valuable because each of these factors can have a significant impact on the patient’s prognosis.

Stage I (T1, N0, M0)

Mesothelioma involves either the right or left pleura lining the chest. It has only spread to the outer lining of the lung in, at most, a few small spots. It has not spread to the lymph nodes or distant sites.

Stage II (T2, N0, M0)

Mesothelioma involves either the right or left pleura lining the chest and has spread from the lining of the chest into 1) the outer lining of the lung, 2) the diaphragm, or 3) into the lung itself. It has not spread to the lymph nodes or distant sites.

Stage III (T1 or 2, N1 or 2, M0; OR T3, N0-2, M0)

Mesothelioma involves either the right or left pleura lining the chest and may or may not have spread from the lining of the chest into 1) the outer lining of the lung, 2) the diaphragm, 3) into the lung itself and has spread to lymph nodes anywhere in the chest on the same side as the tumor, but has not spread to distant sites; OR Mesothelioma involves either the right or left pleura lining the chest and has spread into 1) the first layer of the chest wall, or 2) the fatty part of the mediastinum, or 3) a single place in the chest wall or 4) the outer covering layer of the heart and may or may not have spread to lymph nodes but not as far as to lymph nodes near the collarbone or on the opposite side of the chest. It has not spread to distant sites.

Stage IV (T4, any N, M0; OR any T, N3, M0; OR any T, any N, M1)

Mesothelioma involves either the right or left pleura lining the chest and has spread 1) into the chest wall, either muscle or ribs, 2) through the diaphragm, 3) into any organ contained in the mediastinum (esophagus, trachea, thymus, blood vessels), 4) into the spine, 5) across to the pleura on the other side of the chest, 6) through the heart lining or into the heart itself, or 7) into the brachial plexus (nerves leading to the arm), and may or may not have spread to lymph nodes anywhere, but has not spread to distant sites; OR the tumor is of any size, but has spread to lymph nodes near the collarbone on either side, to hilar or mediastinal lymph nodes on the side opposite the cancerous lung but not to distant sites; OR the mesothelioma has spread to distant sites.