Malignant Mesothelioma Stages

After malignant mesothelioma is diagnosed, the next step is to try to figure out if it has spread, and if so, how far. This process is called staging. The stage of a cancer describes how much cancer is in the body. It helps determine how serious the cancer is and how best to treat it. Doctors also use a cancer's stage when talking about survival statistics.

The stages of mesothelioma range from I (1) through IV (4). As a rule, the lower the number, the less the cancer has spread. A higher number, such as stage IV, means cancer has spread more. And within a stage, an earlier letter (after the number) means a lower stage. Each person with cancer is unique, but cancers with similar stages tend to have a similar outlook and are often treated in much the same way.

How is the stage determined?

Malignant pleural mesothelioma (MPM), the most common type, is the only mesothelioma that has a formal staging system. These mesotheliomas start in the pleura, which includes the lining of the lungs and the inner lining of the chest wall.

The staging system most often used for MPM is the American Joint Committee on Cancer (AJCC) TNM system, which is based on 3 key pieces of information:

• The extent (size) of the main tumor (T): How far has cancer spread in the pleura? Has it spread into other nearby pleura or structures? Can it be removed with surgery?
• The spread to nearby lymph nodes (N): Has the cancer spread to nearby lymph nodes?
• The spread (metastasis) to distant sites (M): Has the cancer spread to distant organs, like the bones, liver, the lungs or pleura (lining of the lung) on the other side of the body, or the peritoneum (the lining of the abdomen)?

Numbers or letters after T, N, and M provide more details about each of these factors. Higher numbers mean the cancer is more advanced. Once a person’s T, N, and M categories have been determined, this information is combined in a process called stage grouping to assign an overall stage. For more on this, see Cancer Staging.

The system described below is the most recent AJCC system, effective as of January 2018. It's used only for malignant pleural mesotheliomas. Mesotheliomas starting in other places are less common and do not have formal staging systems.

MPM typically is given a clinical stage based on the results of a physical exam, biopsy, and imaging tests (as described in How Is Malignant Mesothelioma Diagnosed?). If surgery is done, the pathologic stage (also called the surgical stage) is determined by examining the tissue removed during the operation. 

Cancer staging can be complex, so ask your doctor to explain it to you in a way you understand.

Stages of malignant pleural mesothelioma

AJCC Stage	Stage grouping	Stage description*
IA	T1 N0 M0	Mesothelioma is in the pleura lining the chest wall on one side of the chest. It may or may not also affect the pleura lining the diaphragm (the thin breathing muscle below the lungs), the mediastinum (the space between the lungs), or the pleura covering the lung (T1). It has not spread to nearby lymph nodes (N0) or to distant parts of the body (M0).
IB	T2 N0 M0	Mesothelioma is in the pleura lining the chest wall on one side of the chest, as well as in the pleura coating the diaphragm, the mediastinum, and the lung. It also has grown into the diaphragm or the lung itself (T2). It has not spread to nearby lymph nodes (N0) or to distant parts of the body (M0).
	OR
	T3 N0 M0	Mesothelioma has grown into nearby structures but may still possibly be removed (resected) with surgery (T3). The tumor is in the pleura lining the chest wall on one side of the chest, as well as the pleura coating the lung, the diaphragm, and the mediastinum on the same side. It also has grown into at least 1 of the following: The first layer of the chest wall (called the endothoracic fascia) The fatty tissue in the mediastinum A single place in the deeper layers of the chest wall The surface of the pericardium (outer covering layer of the heart) The cancer has not spread to nearby lymph nodes (N0) or to distant parts of the body (M0).
II	T1 or T2 N1 M0	Mesothelioma is in the pleura lining the chest wall on one side of the chest (T1), and it may have grown into the diaphragm or the lung itself (T2). The cancer has spread to nearby lymph nodes on the same side of the body as the main tumor (N1). It has not spread to distant parts of the body (M0).
IIIA	T3 N1 M0	Mesothelioma has grown into nearby structures but may still possibly be removed (resected) with surgery (T3). The tumor is in the pleura lining the chest wall on one side of the chest, as well as the pleura coating the lung, the diaphragm, and the mediastinum on the same side. It also has grown into at least 1 of the following: The first layer of the chest wall ( endothoracic fascia) The fatty tissue between the lungs (in the mediastinum) A single place in the deeper layers of the chest wall The surface of the pericardium (outer covering of the heart) The cancer has spread to nearby lymph nodes on the same side of the body as the main tumor (N1). It has not spread to distant parts of the body (M0).
IIIB	T1-T3 N2 M0	Mesothelioma may or may not have grown into nearby structures, and it may still possibly be removed (resected) with surgery (T1 to T3). The cancer has spread to nearby lymph nodes on the other side of the body, or to lymph nodes above the collarbone (supraclavicular lymph nodes) on either side (N2). It has not spread to distant parts of the body (M0).
	OR
	T4 Any N M0	Mesothelioma has grown too far to be removed completely with surgery (T4). The tumor is in the pleura lining the chest wall on one side of the chest, as well as the pleura coating the lung, diaphragm, and mediastinum on the same side. The tumor also has grown into at least 1 of the following: More than 1 place in the deeper layers of the chest wall, including the muscle or ribs Through the diaphragm and into the peritoneum (the lining around the abdomen) Any organ in the mediastinum (esophagus, trachea, thymus, or blood vessels) The spine Across to the pleura on the other side of the chest Through the heart lining (pericardium) or into the heart itself The cancer may or may not have spread to nearby lymph nodes (any N). It has not spread to distant parts of the body (M0).
IV	Any T Any N M1	Mesothelioma may or may not have grown into nearby structures (any T). It may or may not have spread to nearby lymph nodes (any N). It has spread to distant organs, like the bones, the liver, the lung or pleura on the other side of the body, or the peritoneum (the lining of the abdomen) (M1).

* The following categories may be used, but are not listed on the table above: 

• TX: Main tumor cannot be assessed due to lack of information.
• T0: There's no evidence of a primary tumor.
• NX: Nearby lymph nodes cannot be assessed due to lack of information. 

Resectable versus unresectable cancer

The TNM system groups mesotheliomas into stages that help give doctors an idea about a person’s prognosis (outlook). But for treatment purposes, doctors often use a simpler system, based on whether the cancer is likely to be resectable (where all visible tumor can be removed by surgery) or unresectable (all of the cancer cannot be removed).

In general, most stage I and II mesotheliomas, as well as some stage III, might be resectable, but there are exceptions. Whether the cancer can be removed depends not only on how far the tumor has grown, but also on its subtype (most doctors believe only epithelioid and mixed/biphasic tumors are potentially resectable), where it’s located, and if the patient is healthy enough to have surgery.

Even for resectable mesotheliomas, in most cases cancer cells that can’t be seen are left behind after surgery. Because of this, many doctors use other treatments (radiation therapy and/or chemotherapy) along with surgery when possible.

Other prognostic factors

Stage is an important factor in predicting a person’s prognosis (outlook), but other factors also play a role. Some factors linked to longer survival times include:

• Still being able to carry out normal daily tasks
• Being younger
• Being female
• Having the epithelioid subtype of mesothelioma
• Having normal levels of LDH in the blood
• Having normal levels of red blood cells, white blood cells, and platelets