Malignant mesothelioma (me-zoe-thee-lee-OH-muh) is a rare cancer that occurs in the thin layer of tissue that covers the majority of your internal organs (mesothelium).
Doctors divide mesothelioma into different types based on what part of the mesothelium is affected. Mesothelioma most often affects the tissue that surrounds the lungs (pleura). This type is called pleural malignant mesothelioma. Other, rarer types of mesothelioma affect tissue in the abdomen, around the heart and around the testicles.
Mesothelioma is an aggressive and deadly form of cancer. Mesothelioma treatments are available, but for many people with mesothelioma, a cure is not possible. Instead, treatment for mesothelioma is often focused on keeping you as comfortable as possible.
Symptoms
Signs and symptoms of mesothelioma vary depending on where the cancer occurs.
Pleural mesothelioma, which affects the tissue that surrounds the lungs, causes signs and symptoms that may include:
- Chest pain under the rib cage
- Painful coughing
- Shortness of breath
- Unusual lumps of tissue under the skin on your chest
- Unexplained weight loss
Peritoneal mesothelioma, which occurs in tissue in the abdomen, causes signs and symptoms that may include:
- Abdominal pain
- Abdominal swelling
- Lumps of tissue in the abdomen
- Unexplained weight loss
Other Forms of Mesothelioma
Signs and symptoms of other types of mesothelioma are unclear. Other forms of mesothelioma are so rare that not much information is available. Pericardial mesothelioma, which affects tissue that surrounds the heart, can cause signs and symptoms such as breathing difficulty and chest pains. Mesothelioma of tunica vaginalis, which affects tissue surrounding the testicles, may be first detected as a mass on a testicle.
When to See a Doctor
See your doctor if you have signs and symptoms that may indicate mesothelioma. Signs and symptoms of mesothelioma aren't specific to this disease and, due to the rarity of mesothelioma, are more likely to be related to other conditions. If any persistent signs and symptoms seem unusual or bothersome to you, ask your doctor to evaluate them.
Causes
In general, cancer begins when a series of genetic mutations occur within a cell, causing the cell to grow and multiply out of control. It isn't clear what causes the initial genetic mutations that lead to mesothelioma, though researchers have identified factors that may increase the risk. It's likely that cancers form because of an interaction between many factors, such as inherited conditions, your environment, your health conditions and your lifestyle choices.
Mesothelioma Doesn't Include a Noncancerous Tumor
A form of noncancerous (benign) tumor that can occur in the chest is sometimes called benign mesothelioma. However, this name is misleading. Benign mesothelioma doesn't begin in the same cells where the cancerous forms of mesothelioma begin. And, in a minority of cases, benign mesothelioma can be very aggressive, despite the term "benign." For this reason, some doctors now refer to this tumor as solitary fibrous tumor.
Solitary fibrous tumor usually doesn't cause signs and symptoms. Most cases are inadvertently discovered during tests and procedures for other conditions. It isn't clear what causes solitary fibrous tumors, but they aren't linked to asbestos exposure. Treatment for solitary fibrous tumor typically includes surgery.
Risk factors
Asbestos Exposure: The Primary Risk Factor for Mesothelioma
Asbestos is a mineral that's found naturally in the environment. Asbestos fibers are strong and resistant to heat, making them useful in a wide variety of applications, such as in insulation, brakes, shingles, flooring and many other products.
When asbestos is broken up, such as during the mining process or when removing asbestos insulation, dust may be created. If the dust is inhaled or swallowed, the asbestos fibers will settle in the lungs or in the stomach, where they can cause irritation that may lead to mesothelioma, though how exactly this happens isn't understood. It can take 20 to 40 years or more for mesothelioma to develop as a result of asbestos exposure.
Some people with years of asbestos exposure never develop mesothelioma. And yet, others with very brief exposure develop the disease. This indicates that other factors may be involved in determining whether someone gets mesothelioma or doesn't. For instance, you could inherit a predisposition to cancer or some other condition could increase your risk.
Possible Risk Factors
Factors that may increase the risk of mesothelioma include:
- Personal history of asbestos exposure. If you've been directly exposed to asbestos fibers at work or at home, your risk of mesothelioma is greatly increased.
- Living with someone who works with asbestos. People who are exposed to asbestos may carry the fibers home on their skin and clothing. These stray fibers can put others in the home at risk of mesothelioma. People who work with asbestos should shower and change clothes before leaving work.
- A monkey virus used in polio vaccines. Some research indicates a link between mesothelioma and simian virus 40 (SV40), a virus originally found in monkeys. Millions of people may have been exposed to SV40 when receiving polio vaccinations between 1955 and 1963, because the vaccine was developed using monkey cells. Once it was discovered that SV40 was linked to certain cancers, the virus was removed from the polio vaccine. Whether SV40 increases the risk of mesothelioma is a point of debate, and more research is needed.
- Radiation. Some research links mesothelioma to the radioactive substance thorium dioxide, which was used along with X-rays to diagnose various health conditions from the 1920s to the 1950s. Mesothelioma has also been linked to radiation therapy treatments to the chest, such as those used to treat breast cancer or lymphoma.
- Family history. A family history of mesothelioma may increase your risk of mesothelioma, but more research is needed to understand this theory.
If you have signs and symptoms that might indicate mesothelioma, your doctor will conduct a physical exam to check for any lumps or other unusual signs. Your doctor may order imaging scans, such as a chest X-ray and a computerized tomography (CT) scan of your chest or abdomen, to look for abnormalities. Based on the findings, you may undergo further testing to determine whether mesothelioma or another disease is causing your signs and symptoms.
Biopsy
Biopsy, a procedure to remove a small portion of tissue for laboratory examination, is the only way to determine whether you have mesothelioma. Depending on what area of your body is affected, your doctor selects the right biopsy procedure for you. Options include:
- Fine-needle aspiration. The doctor removes fluid or a piece of tissue with a small needle inserted into your chest or abdomen.
- Thoracoscopy. Thoracoscopy allows the surgeon to see inside your chest. In this procedure, the surgeon makes one or more small incisions between your ribs. A tube with a tiny video camera is then inserted into your chest cavity — a procedure sometimes called video-assisted thoracoscopic surgery (VATS). Special surgical tools allow your surgeon to cut away tissue for testing.
- Laparoscopy. Laparoscopy allows the surgeon to see inside your abdomen. Using one or more small incisions into your abdomen, the surgeon inserts a tiny camera and special surgical tools to obtain a small piece of tissue for examination.
- Thoracotomy. Thoracotomy is surgery to open your chest between the ribs to allow a surgeon to check for signs of disease. A sample of tissue may be removed for testing.
- Laparotomy. Laparotomy is surgery to open your abdomen to allow a surgeon to check for signs of disease. A sample of tissue may be removed for testing.
The tissue sample is analyzed under a microscope to see whether the abnormal tissue is mesothelioma and what types of cells are involved. The type of mesothelioma you have determines your treatment plan.
Staging
Once mesothelioma is diagnosed, your doctor orders other tests to determine the extent, or stage, of the cancer. Imaging tests that may help determine the stage of your cancer may include:
- Chest X-ray
- CT scans of the chest and abdomen
- Magnetic resonance imaging (MRI)
- Positron emission tomography (PET)
Your doctor determines which tests are more appropriate for you. Not every person needs every test.
Once the extent of pleural mesothelioma is determined, a stage is assigned.
- Stage I pleural mesothelioma is considered localized cancer, meaning it's limited to one portion of the lining of the chest.
- Stage II mesothelioma may have spread beyond the lining of the chest to the diaphragm or to a lung.
- Stage III mesothelioma may have spread to other structures within the chest and may involve nearby lymph nodes.
- Stage IV mesothelioma is an advanced cancer that has spread more extensively within the chest. Stage IV may also indicate that mesothelioma has spread to distant areas of the body, such as the brain and lymph nodes elsewhere in the chest.
Formal stages aren't available for other types of mesothelioma because these types are rare and aren't well studied.
Source: