When you get a mesothelioma diagnosis, your doctor may also tell you what stage of cancer you have. Mesothelioma stages help healthcare professionals understand your diagnosis better. The types of treatment your doctors recommend will be determined, in part, by the stage of your disease at the time of your diagnosis. Understanding mesothelioma stages can help you better understand the disease and to take a more active role in your treatment.
What Are Mesothelioma Stages?
Physicians have developed systems for determining the progression and severity of cancer. These systems are called staging. Your doctor will be able to assess the stage of your mesothelioma cancer after doing tests to determine whether the cancer has spread and how far.
Mesothelioma is a cancer caused by exposure to toxic asbestos fibers. It is a disease of the membranes that surround and protect your organs. These membranes are called mesothelium. There are four mesothelioma types: pleural (affecting the lining around the lungs), peritoneal (the lining around the organs in the abdomen), pericardial (the sac that surrounds and protects the heart) and testicular (the lining within the testicles).
While doctors can determine mesothelioma stages for pleural mesothelioma (the most common form of the disease), they may not be able to stage peritoneal, pericardial, or testicular mesothelioma. This is not because those mesothelioma types don’t progress over time. They are simply so uncommon that researchers don’t know enough about how these types of mesothelioma spread. They are not able to describe what happens at each stage in the progression of the disease, so they don’t assign a stage to the tumor.
Mesothelioma stages give medical professionals a way to talk about cancers that is widely understood. Determining mesothelioma stages is also helpful because researchers collect data on outcomes and survival rates for mesothelioma patients based on the stage at which they were diagnosed. In this way, your mesothelioma diagnosis also contributes to scientific understanding of the disease.
The Meaning of Mesothelioma Stages
The most comprehensive system used to define mesothelioma stages is called TNM. The acronym stands for: Tumor Nodes Metastasis.
The TNM system was first developed by the American Joint Committee on Cancer (AJCC) and this medical organization creates and updates the guide for using this staging system. The Union for International Cancer Control (UICC) also endorses the TNM system.
In the mid-1990s, the International Mesothelioma Interest Group (iMig) used the TNM foundation to describe mesothelioma stages. These stages are most clearly described for pleural mesothelioma, since that form of the disease accounts for almost three quarters of mesothelioma cases.
The T stage refers to the original tumor. The N stage involves spread to the lymph nodes. In the M stage, the cancer has spread or metastasized. Each stage in the TNM system of mesothelioma stages is also divided into sub-stages for more precise classification.
In the T mesothelioma stages, the cancer is limited to the area of the original tumor. Here are the T stages for pleural mesothelioma:
- TX stage: doctors can’t evaluate the tumor. This may be because it is too small to easily evaluate or because it’s in a spot that is difficult to access for diagnosis.
- T0 stage: doctors can’t locate a primary tumor at all. This is a very early stage of mesothelioma cancer.
- T1 stage: the cancer is on just one side of the body, occurring in the parietal pleura. The parietal pleura is the outer layer of the mesothelial tissue (called a pleura) that surrounds the lungs. At this stage, the cancer may have spread to the diaphragm or may be limited to the pleura.
- T1a stage: The visceral pleura is not affected by mesothelioma cancer. The visceral pleura is the inner layer of the mesothelium around the lungs. This part of the pleura clings to the surface of the lungs.
- T1b stage: The cancer has reached the visceral pleura.
- T2 stage: In this stage, mesothelioma has spread throughout the pleura and affects at least one of these nearby body parts:
- The diaphragm.
- The lung tissue below the visceral pleura. The part of the lung affected at this stage is the parenchyma – the parts of the lung that transfer oxygen into the bloodstream and remove carbon dioxide and other waste gases.
- T3 stage: The cancer now involves all the layers of the pleura. It is can also be found in one or more of these areas near the original tumor:
- The connective tissues between the ribs and the fatty tissue in the chest.
- A single tumor that reaches into the wall of the chest.
- A single layer of the pericardium, which is the lining or mesothelium around the heart.
- T4 stage: This stage describes a progression where the mesothelioma involves every layer of the pleura and at least one of these other spots:
- Multiple tumor masses are spread out in small, diffuse nodes on the chest wall. At this stage, the cancer may have started to attack one or more of the ribs.
- The diaphragm is involved and the cancer has spread from there into the peritoneum, the mesothelium or lining that protects your abdomen.
- The tumor has grown into another organ in the chest cavity or into the spine.
- Mesothelioma has crossed the midline of the body and affects the pleura of the second lung as well.
- The tumor has grown through all the layers of the pericardium and may have reached the heart muscle or caused fluid buildup around the heart.
In the N mesothelioma stages, the lymph nodes are involved.
- NX stage: Your doctor can’t tell whether the cancer has spread to the lymph nodes or not.
- N0 stage: There is no cancer in the adjacent lymph nodes.
- N1 stage: Mesothelioma has spread to the lymph nodes near your lungs.
- N2 stage: The cancer has spread to lymph nodes near the trachea or windpipe, the mediastinal nodes in the center of the chest cavity near the original tumor, or the nodes near the breasts or diaphragm. In this mesothelioma stage, the involved lymph nodes are on the same side of the body as the original tumor.
- N3 stage: Lymph nodes on the side of the body opposite the original tumor are involved. This can include lymph nodes in the mediastinum or breasts. The lymph nodes above the collar bone can also be involved, either on the original side of the body or the opposite side.
Two medical terms you might find helpful to understand mesothelioma stages are ipsilateral and contralateral. Ipsilateral means on the same side of the body as the original tumor. Contralateral means the opposite side. Once cancer spreads across the midline of the body to the opposite side, the cancer is considered to be at a more advanced stage and treatment is more difficult.
There are just two M mesothelioma stages. These stages indicate that the cancer has metastasized or migrated to form tumors in other parts of the body.
- M0 stage: Although the cancer has spread, it is confined to parts of the body near where the original tumor was located.
- M1 stage: Cancer has spread to far-removed areas of the body.
Your cancer may be described as Stages I through IV, using a combination of these TNM stages. Here is how those mesothelioma stages break down:
- Stage I: T1 (the tumor is in the pleura, on one side of the body, and may have spread to the diaphragm), N0 (no spread to lymph nodes), M0 (no metastasis)
- Stage II: T2 (spread to the diaphragm or the lungs or both), N0, M0
- Stage III: T1 or T2 and N1 or N2 (spread to lymph nodes, still on the same side of the body), M0. Stage III pleural mesothelioma can also by T3 (spread to other parts of the chest) with or without lymph node involvement (N0, N1, or N2)
- Stage IV: T4 (major tumor spread, possibly contralateral or on the other side of the body) with any N stage and M0 or any T stage with N3 (contralateral lymph nodes affected) and M0 or any T stage and any N stage with M1 (metastatic tumors formed in far-removed areas of the body).
Understanding the aggressiveness of the disease can help mesothelioma doctors determine what tools to use to fight it. All cancer treatments have some side effects, so your medical team will use the mesothelioma stages to weigh the benefits and dangers of different mesothelioma treatment options.
Other Ways to Determine Mesothelioma Stages
In 1976, Dr. Eric G. Butchart developed the first system to describe mesothelioma stages. His four-stage system didn’t take into account all the factors that are considered in the TNM systems, though there are many similarities. The Butchart staging system is no longer widely used, but it provided an important foundation on which the modern understanding of mesothelioma stages has been built.
In addition to mesothelioma stages, your mesothelioma diagnosis may also include a description of the type of cancer cells in your tumor, the location of your tumor (which can affect treatment options and the complexity of your case), and the amounts of certain tumor markers found in a blood test. Some mesothelioma tumors are also given a grade. The grade is determined by examining cells from your tumor under a microscope. Doctors grade the tumor by how abnormal the cells appear. The more unusual the cells, the quicker the cancer tends to spread.
What Do Mesothelioma Stages Mean for You?
Your doctor will, if possible, determine how far your mesothelioma cancer has progressed at the time you are diagnosed. He will choose from among the mesothelioma stages described above. The staging assigned to your cancer is part of your diagnosis, not a description of the progression of the disease.
During treatment, your mesothelioma may progress. A Stage I or T2 stage tumor may invade the lymph nodes. At a later point, a metastatic tumor may be found in a different part of the body. Your mesothelioma stage, however, does not change. If you were diagnosed with Stage I pleural mesothelioma and it spreads to your liver, the second cancer will be called metastatic Stage I pleural mesothelioma.
Staging can also reflect the aggressiveness of the cancer cells in your particular tumor. Even if you catch it early, a fast-moving mesothelioma tumor may be diagnosed as Stage II or Stage III.
How Are Mesothelioma Stages Determined?
Mesothelioma is not a simple disease to diagnose. Once it is diagnosed, it may be hard to determine which of the mesothelioma stages it has progressed to.
For the rarer types of mesothelioma (testicular and pericardial), there simply have not been enough cases to determine mesothelioma stages. Medical researchers need more data to determine the usual progression of each mesothelioma type.
Although there are more cases of peritoneal mesothelioma, this form of the disease may be difficult to type as well. Sometimes doctors do not give a stage when they diagnose mesothelioma.
To determine the stage of pleural mesothelioma, your doctor will examine you, ask you questions about your symptoms, and order medical tests. These may be some of the same tests that are used to detect the presence of a tumor and determine the mesothelioma type. This is known as clinical staging.
CT scans, MRIs, and PET scans can all be useful in determining if the mesothelioma tumor has metastasized to nearby organs or other parts of the body. Your surgeon may need to remove some of your lymph nodes to determine whether the mesothelioma has spread to the lymph nodes and the extent of that spread.
Your mesothelioma might be staged pathologically if you’ve had a biopsy or if your tumor has been surgically removed as part of the diagnostic process. This means that your doctors will take the results of your imaging tests and combine them with information they learn from the tissues samples in order to determine which of the mesothelioma stages best describes your situation. Pathological examination of your mesothelioma tumor could include examination under a microscope or sending samples to the lab for further testing.
Examination of cells from the tumor after a biopsy can also determine the grade of the cancer. This grade tells your doctors how aggressive or fast-moving your tumor is.
Mesothelioma stages are just one diagnostic tool. They help your medical team recommend the best treatment options for you, based on the status of your mesothelioma cancer at the time it is discovered. These recommendations are based on past experience with other mesothelioma patients and medical research on patients at different mesothelioma stages. Your experience may not be exactly the same as someone else with the same type and stage of mesothelioma.