Mesothelioma is a type of cancer caused by asbestos exposure. It affects the thin membrane that protects several of the body's most important organs, including the abdomen, lungs, and heart. This membrane is called the mesothelium. When the cancer cells spread to parts of the body outside of the original location of the primary tumor, the cancer is called metastatic mesothelioma.
Several factors influence mesothelioma metastasis, including response to treatment and cell type. If you have mesothelioma, it’s helpful to know how the cancer spreads and how to get the support you need for the appropriate treatment.
What Is Mesothelioma Metastasis?
Mesothelioma metastasis refers to the spread of mesothelioma throughout the body. The primary tumor will likely originate in one of four places:
- Pleura: The lining of the lungs.
- Peritoneum: The lining around the abdominal cavity.
- Pericardium: The membrane around the heart.
- Testes: The testicular glands in the scrotum in patients with male genitalia.
Mesothelioma Metastasis vs. Metastatic Mesothelioma
Mesothelioma metastasis and metastatic mesothelioma both refer to the spread of mesothelioma cancer cells from the primary site to other parts of the body.
Where & When Does Mesothelioma Metastasize?
Mesothelioma cells can metastasize at any stage of the disease. Metastasis itself can be divided into one of three stages: local, regional, and distant.
- Local metastasis occurs when the tumor cells spread outside of the primary tumor location but haven’t affected other parts of the body.
- Regional metastasis occurs when the tumor cells have spread to parts of the body near the primary tumor location.
- Distant metastasis occurs when cancer cells break away from the primary tumor and travel through the bloodstream or lymphatic system to establish secondary tumors in distant organs or tissues. These distant sites are often far from the primary tumor. For example, in mesothelioma, distant metastasis may involve the spread of cancer cells to the liver, bones, adrenal glands, or other organs. Distant metastases occurs in 10% to 50% of stage four mesothelioma cases. It is sometimes referred to as systemic metastasis.
In early-stage mesothelioma, metastasis is generally local or regional. Late-stage mesothelioma, in contrast, generally refers to distant metastasis. The different stages of metastasis can look different based on the different types of mesothelioma.
Malignant Pleural Mesothelioma
Pleural mesothelioma primarily originates in the thin layer of tissue that lines the interior wall of the chest cavity and covers the lungs. This tissue is called the pleura. About 75 to 80% of mesothelioma diagnoses are pleural, making it the most common type of mesothelioma. Malignant pleural mesothelioma is usually local and rarely involves distant metastasis.
Peritoneal mesothelioma occurs in the membrane that lines the abdominal and pelvic cavity and surrounds the abdominal organs. This membrane is called the peritoneum. Peritoneal mesothelioma is the second most common type of mesothelioma, occurring in about 10 to 20% of mesothelioma diagnoses.
Local and regional metastasis for peritoneal mesothelioma means that the cancer cells have spread to nearby locations in the body, such as the lymph nodes, liver, kidneys, or adrenal glands. Distant metastasis for peritoneal mesothelioma, in contrast, means that the cancer cells have spread to distant parts of the body, such as bones, the thyroid, pancreas, or central nervous system.
Pericardial mesothelioma occurs in the fibrous sac that encloses the heart and great vessels. This sac is called the pericardium. Pericardial mesothelioma is a rare type of mesothelioma, diagnosed in fewer than 1% of mesothelioma cases. Information about this type of mesothelioma is more limited.
Testicular mesothelioma occurs in a membrane that covers the testes called the tunica vaginalis. This type of mesothelioma is diagnosed in fewer than 1% of mesothelioma cases. . Metastasis is rare for this type of mesothelioma. When it does occur, it tends to spread to the thoracic and lumbar vertebrae, omentum, liver, and lungs.
Factors That Impact Metastatic Mesothelioma
Several factors may impact the likelihood that mesothelioma cells will metastasize. These factors include the cell type affected by the cancer, the cells’ response to treatment, and the stage of mesothelioma. Patients with earlier-stage diagnoses tend to have better outcomes from treatment—especially if they are diagnosed with a cell type that responds well to treatment.
There are three different cell types of mesothelioma: sarcomatoid, epithelioid, and biphasic. Epithelioid cells are less likely to be aggressive and less prone to metastasis. This cell type is also generally associated with a longer life expectancy.
Sarcomatoid cells tend to spread faster and are more prone to metastasis than epithelioid cells. They are also less responsive to treatment which can reduce life expectancy.
Both sarcomatoid and epithelioid cells occur in biphasic mesothelioma. As a result, biphasic mesothelioma is sometimes referred to as mixed type. The ratio of each cell type can affect treatment options and treatment response. Patients with more epithelial cells than sarcomatoid cells are more likely to have a better prognosis.
Response to Treatment
If the mesothelioma cells respond well to treatment, the metastasis process tends to slow down. Treatments that eliminate cancer cells may be able to stop metastasis altogether. However, if the mesothelioma cells do not respond well to treatment, then treatment is likely to do little to slow or stop the metastasis process.
More aggressive mesothelioma treatments are often available to earlier-stage patients. These tend to have the biggest impact on stopping or slowing metastasis. Treatments that can kill cancer cells include radiation therapy, immunotherapy, and chemotherapy. In combination with one or more of these treatments, surgery may be performed to remove as much of the cancer as possible.
Early-Stage vs. Late-Stage
Cancer stage can have a profound impact on mesothelioma metastasis. Oncologists use a mesothelioma staging system known as the TNM staging system. T describes the extent of the tumor; L describes the involvement of the lymph nodes; and M describes the metastasis). The TNM staging system is most commonly used to provide a prognosis for pleural mesothelioma.
If early-stage mesothelioma has metastasized, the metastasis is usually local or regional. Patients with early-stage mesothelioma have access to more aggressive and invasive treatment options. These treatment options are used to remove as much mesothelioma cancer from the body as possible.
Late-stage mesothelioma patients are at a higher risk of metastasis. When mesothelioma spreads, it is more difficult to treat. Patients with late-stage mesothelioma generally have fewer treatment options. In addition, they’re likely to have weaker immune systems, and their bodies may not be able to handle more aggressive treatments.
Metastatic Mesothelioma FAQs
What are the treatment options for metastatic mesothelioma?
There are a variety of treatment options available for mesothelioma patients. Doctors who specialize in treating mesothelioma will recommend a treatment plan based on the type of mesothelioma diagnosed, the cancer stage, and the patient’s age and overall health. Treatment options are generally either palliative or potentially curative.
Palliative care is mainly focused on reducing pain and other symptoms and on improving the overall quality of life. Palliative care may include chemotherapy, radiation therapy, surgery, and immunotherapy. Palliative surgery may be performed for late-stage mesothelioma patients. This type of surgery can ease the symptoms of mesothelioma and improve the quality of life.
Potentially curative care is used for early-stage patients who are otherwise in good health. Potentially curative surgery can improve prognosis by removing as much cancer from the body as possible. Doctors may combine surgery with other forms of treatment, such as radiation or chemotherapy.
How is metastatic mesothelioma diagnosed?
Mesothelioma specialists use an array of tests to help diagnose mesothelioma and to determine staging. These tests help specialists obtain a more accurate picture of the cancer stage, as well as identify the location of the mesothelioma tumor. Some examples of diagnostic tests include blood tests, imaging scans, and biopsies, and CT scans and PET scans can be helpful in determining the appropriate stage.
Blood tests: Blood tests can show if you have certain proteins in your blood that indicate the possible presence of mesothelioma. Blood tests are not accurate for diagnosing mesothelioma, but they can help doctors decide whether to order additional diagnostic tests.
Imaging tests: A variety of imaging tests can be used to help diagnose mesothelioma. An X-ray is often used first. It produces a two-dimensional image of the affected area and shows the tumors and buildups of fluid in the peritoneal or pleural cavities. If the X-ray reveals an accumulation of fluid or a tumor, then the doctor is likely to order another imaging test, such as a CT scan. A CT scan helps to provide a clearer picture of an area of the body. A CT scan can also be used to find diseased tissue that is suitable for biopsy. MRI scans and PET scans are useful in helping doctors determine if the cancer has metastasized to other parts of the body. An echocardiogram might also be used to create pictures of the heart. It can help diagnose pericardial mesothelioma.
Biopsies: Mesothelioma can be diagnosed using biopsies. A biopsy is a tissue or fluid sample taken from a patient who might have mesothelioma. Pathologists analyze the sample to differentiate mesothelioma cells from other types of cancer. The recommended biopsy procedure depends on several factors, including the location of the original tumor and the degree of metastasis.
Once a mesothelioma diagnosis has been confirmed, a specialist will create a course of treatment that is tailored to the patient's diagnosis.
How does metastasis impact a mesothelioma patient’s prognosis and life expectancy?
Mesothelioma patients with metastasis that is local or regional have a better life expectancy and prognosis than those with distant metastasis. This is because local and regional metastasis is generally associated with early-stage mesothelioma. Patients with early-stage mesothelioma have access to more aggressive treatment options which have the potential to remove as much mesothelioma from the body as possible.
In contrast, late-stage diagnoses and distant metastasis often have a worse prognosis and life expectancy. Patients in this category are more likely to have a weakened immune system and may have fewer treatment options.
Discover How You Can Beat The Odds with Our Mesothelioma Guide
If you or a loved one has been diagnosed with mesothelioma, it’s important to learn about the disease, including mesothelioma metastasis, to more clearly understand the diagnosis and available treatments. The Mesothelioma Group is committed to providing patients and their loved ones with up-to-date, well-researched, and accurate information about mesothelioma and its treatment. We can even provide questions to ask your doctor so you better understand your treatment plan.
You can use our free mesothelioma guide to get answers to your most frequently asked questions. The guide includes information on the latest treatments, strategies for covering the cost of treatment, and ways to improve life expectancy. You may also contact us at (800) 333-8975.