Mesothelioma Staging

The most commonly used staging system was developed by the American Joint Committee on Cancer (AJCC). This is a TNM system, similar to staging systems used for most other cancers. T stands for tumor (the size of the primary tumor and how far it has spread to nearby organs), N stands for spread to lymph nodes, and M is for metastasis (spread to distant organs). In TNM staging, a number between 0 and 4 follows each of the letters, with higher numbers indicating increasing severity. Then the 3 letter and number combinations are combined to a stage indicated by a Roman numeral between I and IV. Tumors in similar stages tend to behave in similar ways and need similar treatment. The lower the stage number, the better the outlook. Minor differences exist between the AJCC TNM staging system and the Butchart staging system.Like the Butchart System, this system is for staging pleural mesotheliomas There is more information in the AJCC system than the other two systems. From the American Joint Committee on Cancer, last reviewed 3/17/09:

• T indicates the extent of spread of the main (primary) tumor.
• N describes how much the cancer has spread to nearby (regional) lymph nodes. Lymph nodes are small bean-shaped collections of immune system cells that are important in fighting infections.
• M indicates whether the cancer has spread (metastasized) to other organs of the body. (The most common sites are the pleura on the other side of the body, the lungs, and the peritoneum.)

Numbers or letters appear after T, N, and M to provide more details about each of these factors. The numbers 0 through 4 indicate increasing severity.

T groups

T1: Mesothelioma involves either the right or left pleura lining the chest wall or diaphragm. It may or may not have spread to small spots on the pleura covering the lung as well.
T2: Mesothelioma involves either the right or left pleura lining the chest wall or diaphragm, and has grown into at least one of the following:

• a large area of the pleura lining the lung
• the diaphragm
• the lung itself

T3: Mesothelioma involves either the right or left pleura lining the chest wall, lung, or diaphragm and has grown into at least one of the following:

• the first layer of the chest wall
• the fatty part of the mediastinum (space between the lungs)
• a single place in the deeper layers of the chest wall
• the pericardium (outer covering layer of the heart)

T4: Mesothelioma involves either the right or left pleura lining the chest wall, lung, or diaphragm and has grown into at least one of the following:

• the deeper layers of the chest wall, including the muscle or ribs
• through the diaphragm and into the peritoneum
• any organ in the mediastinum (esophagus, trachea, thymus, blood vessels)
• the spine
• across to the pleura on the other side of the chest
• through the heart lining or into the heart itself
• the brachial plexus (a collection of nerves leading to the arm)

N groups

N0: No spread to lymph nodes.
N1: Spread to lymph nodes within the lung and/or around the area where the bronchus enters the lung (hilar lymph nodes) on the same side as the mesothelioma.
N2: Spread to lymph nodes around the carina (point where the windpipe branches into the left and right bronchi) and/or in the space behind the breastbone and in front of the heart (mediastinum). Affected lymph nodes are on the same side as the primary tumor.
N3: Spread to lymph nodes near the collarbone on either side, and/or spread to hilar or mediastinal lymph nodes on the side opposite the primary tumor.

M groups

M0: No spread to distant organs or areas.
M1: The cancer has spread to distant sites. This can be to distant lymph nodes or to other organs.

Stage grouping for pleural mesothelioma
Once the T, N, and M categories have been assigned, this information is combined in a process called stage grouping to assign an overall stage of I, II, III, or IV. The stages identify tumors that have a similar prognosis and thus are treated in a similar way. Patients with lower stage numbers tend to have a better prognosis.

Stage I
T1, N0, M0: Mesothelioma involves either the right or left pleura lining the chest wall or diaphragm. It may or may not have spread to small spots on the pleura covering the lung as well. It has not spread to the lymph nodes or to distant sites.

Stage II
T2, N0, M0: Mesothelioma involves either the right or left pleura lining the chest wall or diaphragm and has grown into a large area of the pleura lining the lung, the diaphragm, or the lung itself. It has not spread to the lymph nodes or to distant sites.

Stage III  There are 2 combinations of categories that make up this stage.

T1 or T2, N1 or N2, M0: Mesothelioma involves either the right or left pleura lining the chest and may or may not have grown into the pleura lining the lung, the diaphragm, or into the lung itself. It has spread to lymph nodes in the chest on the same side as the tumor. It has not spread to distant sites.
T3, N0-2, M0: Mesothelioma involves either the right or left pleura lining the chest and has grown into the first layer of the chest wall, the fatty part of the mediastinum, a single place in the deeper layers of the chest wall, or the outer covering layer of the heart. It may or may not have spread to lymph nodes in the chest on the same side as the tumor but has not spread to lymph nodes near the collarbone or on the opposite side of the chest. It has not spread to distant sites.

Stage IV There are 3 combinations of categories that make up this stage.

T4, any N, M0: Mesothelioma involves either the right or left pleura lining the chest and has spread into the deeper layers of the chest wall (including the muscle or ribs), through the diaphragm and into the peritoneum, into any organ in the mediastinum, into the spine, across to the pleura on the other side of the chest, through the heart lining or into the heart itself, or into the brachial plexus. It may or may not have spread to lymph nodes. It has not spread to distant sites
Any T, N3, M0: The tumor is of any size. It has spread to lymph nodes near the collarbone on either side and/or to hilar or mediastinal lymph nodes on the side opposite the primary tumor. It has not spread to distant sites
Any T, any N, M1: The mesothelioma is of any size and may or may not have spread to the lymph nodes. It has spread to distant sites.
 

The oldest system used for measuring mesothelioma staging is the Butchart Staging System. This staging procedure is only used for pleural mesothelioma (cancer of the lining of the lungs) because it is by far the most common type of mesothelioma.

Stage 1 – Localized Malignant Mesothelioma

Stage I mesothelioma is the initial stage of mesothelioma. Here, the cancerous tumor is found in the pleura (the lung lining), and may also involve the diaphragm.

Stage 2 Mesothelioma

In Stage II mesothelioma, in addition to the presence of mesothelioma in pleura on one side, it may have spread to the other side, and also moved into the stomach, the pleura, esophagus, or heart on both sides. Also, mesothelioma may have spread to the lymph nodes in the chest.

Stage 3 Mesothelioma

In Stage III, mesothelioma has invaded the diaphragm into the peritoneum (the lining of the abdomen), and may involve lymph nodes outside of the chest.

D. Stage 4 Mesothelioma

In Stage IV, mesothelioma has metastasized, spreading through the bloodstream to other organs of the body.

Finally, The Brigham System is the newest of the three staging systems. It looks at the cancer from the perspective of surgical removability, so it is rarely used. Most mesotheliomas are found too late to be able to resect them. Stage 1 – The mesothelioma is still resectable (can be removed surgically ) and no lymph nodes are affected.

Stage 2 – The tumor is still resectable, but lymph nodes are affected.

Stage 3 – The mesothelioma is not resectable, and it has penetrated the heart, chest wall, abdominal cavity or diaphragm. Lymph nodes may or may not be involved.

State 4. – The mesothelioma is not resectable and has metastasized, spread throughout the body.

With all of the systems, stage one is considered local, while other stages are considered advanced.

Anna L. Kaplan, M.D.