It is a cancer that begins in the cells of the lining of certain parts of the body, especially the lining of the chest or abdomen.
Cancer begins when cells start to grow out of control. Cells in almost any part of the body can turn into cancer.
A layer of specialized cells called mesothelial cells lines the inside of your chest, abdomen, and the space around your heart.
These cells also cover the outer surface of most of your internal organs. The lining formed by these cells is called the mesothelium.
The mesothelium helps protect your organs by making a special lubricating fluid that allows the organs to move against each other. For example, this fluid makes it easier for your lungs to move (expand and contract) within your chest when you breathe.
The mesothelium has different names on different parts of the body:
- The pleura lines the lungs and the space in the chest that contains the lungs.
- The peritoneum lines the inside of the abdomen and many of the organs in the abdomen.
- The pericardium covers the heart and creates the space that holds the heart in the chest.
- The tunica vaginalis covers the testicles.
Mesothelial tumors can start in any of these linings. These tumors can be non-cancerous (benign) or cancerous (malignant).
A cancerous tumor of the mesothelium is called a malignant mesothelioma, although it is often reduced to just mesothelioma.
Mesotheliomas can start in 4 main areas of the body.
- Pleural mesotheliomas start in the chest. About 3 out of 4 mesotheliomas are pleural mesotheliomas.
- Peritoneal mesotheliomas start in the abdomen. They make up the majority of the remaining cases.
- Pericardial mesotheliomas start in the covering around the heart and are very rare.
- Tunica vaginalis mesotheliomas are very rare tumors that begin in the lining layer of the testicles.
Malignant mesotheliomas can also be classified into 3 main types based on how cancer cells are organized:
- About half of mesotheliomas are epithelioid. This type tends to have a better outlook (prognosis) than the other types.
- About 10% of mesotheliomas are sarcomatoid (fibrous).
- Mixed (biphasic) mesotheliomas have epithelioid and sarcomatoid areas. They make up the remaining 30% to 40% of mesotheliomas.
Benign tumors of the mesothelium
Benign (non-cancerous) tumors can also start in the mesothelium. These tumors are usually removed by surgery, and there is often no need for additional treatment.
Localized fibrous tumor of the pleura
This type of benign tumor can form in the pleura that surrounds the lungs. It used to be called benign fibrous mesothelioma, but now doctors know that this tumor does not actually start in the mesothelial cells.
This disease is generally benign, but about 1 in 10 is cancerous. A similar condition that begins in the peritoneum is called a solitary fibrous tumor of the peritoneum.
This benign tumor can develop in the mesothelium of certain reproductive organs.
In men, it often begins in the epididymis (tubes that carry sperm cells out of the testicle).
In women, this tumor can start in the fallopian tubes (tubes that carry eggs from the ovaries to the uterus).
Benign cystic mesothelioma
This rare non-cancerous tumor often begins in the peritoneum.
Signs and symptoms of mesothelioma
Many of the early symptoms of mesothelioma are more likely to be caused by other conditions, so people may initially ignore or mistake them for common and minor ailments. Most people with mesothelioma have symptoms for at least a few months before they are diagnosed.
Symptoms of pleural mesothelioma (mesothelioma of the chest) can include:
- Pain in the side of the chest or lower back.
- Short of breath.
- Excessive sweating
- Weight loss (without trying).
- Swallowing problems (feeling that food is stuck).
- Swelling of the face and arms.
Symptoms of peritoneal mesothelioma can include:
- Abdominal (belly) pain.
- Swelling or fluid in the abdomen.
- Weight loss (without trying).
- Nausea and vomiting
- Constipation .
These symptoms can be caused by mesothelioma, but are most often caused by other conditions. Still, if you have any of these problems (especially if you’ve been exposed to asbestos), it’s important to see your doctor right away so the cause can be found and treated, if necessary.
A cause is the contributing factor that leads to a disease or health condition.
Inhalation or ingestion of microscopic asbestos fibers is responsible for most cases of mesothelioma.
In rare cases, exposure to radiation and exposure to zeolite, another type of fibrous mineral similar to asbestos, have been identified as the causes of mesothelioma.
A risk factor in this case is anything that increases the chances of developing mesothelioma or asbestos-related cancers.
Factors that increase the risk of mesothelioma from asbestos exposure include:
- Working in an asbestos mine or asbestos processing plant.
- Working in high-risk occupational settings, such as construction or the automotive industry.
- Serving on military ships or facilities built with asbestos-containing products.
- Living in a residential area near an asbestos mine.
- Disruptive asbestos products during a home renovation without proper safety measures.
In addition to the risk factors associated with asbestos, there are other factors that could increase your risk of developing mesothelioma or another asbestos-related disease.
Exposure to mineral fibers
Exposure to the fibrous mineral zeolite can increase the risk of mesothelioma.
Exposure to radiation
Exposure to radiation can increase the risk of mesothelioma, but the evidence is rare and inconsistent.
Several studies have shown that the risk of mesothelioma increases slightly after a person receives radiation therapy as a treatment for other cancers.
Polio and Simian Virus Vaccines 40
Some studies suggest that people who received a polio vaccine between 1955 and 1963 may have an increased risk of developing mesothelioma.
Tens of millions of doses of polio vaccine during that nine-year period were inadvertently contaminated with simian virus 40 (SV40).
Although the largest studies found no link between the virus and increased risk of mesothelioma, the issue remains controversial as studies continue.
Because only a small number of people exposed to asbestos develop mesothelioma, scientists believe that genetics may play a role in a person’s risk. Researchers have confirmed that a mutation in a gene called BAP1 increases the likelihood of developing mesothelioma and other cancers.
If someone else in your family has mesothelioma, genetic testing may suggest that you have an increased risk of developing cancer.
Age and gender
Mesothelioma is more commonly diagnosed in men than women and rarely affects people under 45 years of age. This is because mesothelioma often takes decades to develop, and men are more likely to work in places where asbestos exposure occurs.
Is smoking a risk factor for mesothelioma?
Studies show that smoking is not a risk factor for mesothelioma, but those who smoke and are regularly exposed to asbestos are much more likely to develop asbestos-related lung cancer.
Some studies reveal that the combination of smoking and asbestos exposure increases the risk of lung cancer by about 90 percent.
The researchers also found that smoking can weaken the lungs and reduce the body’s ability to rid itself of asbestos fibers trapped inside. Smoking also aggravates asbestosis, an incurable respiratory disorder also caused by exposure to asbestos.
A risk factor for mesothelioma is not necessarily a cause. Rare causes, such as exposure to radiation and zeolite, could also be considered risk factors.
Although research shows that men are much more likely to develop mesothelioma than women, gender alone cannot cause cancer. The same can be true for other risk factors.
Multiple risk factors can increase your risk of developing mesothelioma.
The duration of the exposure also plays a key role. While the World Health Organization says that no amount of asbestos exposure is considered safe, it is usually repeated, heavy exposures over many years that lead to mesothelioma and other asbestos-related diseases.
The link between asbestos exposure and mesothelioma is so strong that it can be difficult for researchers to know whether other known risk factors alone can cause mesothelioma.
Although scientists continue to study this topic, asbestos exposure remains the clearest cause of mesothelioma.
Where does exposure to asbestos occur?
Asbestos once filled countless homes and businesses. In the form of insulating and thermal protection materials. Asbestos was a key element in thousands of household and industrial products, including drywall, wiring, glues and adhesives, roof tiles, cements, and shingles.
Some of these asbestos products remain in old structures and are generally harmless as long as they are not disturbed.
Workers were generally exposed to the harmful natural mineral while working, but others, including family members, also faced secondary exposures at home and environmental exposures in communities that mined or processed asbestos.
Occupations that are at high risk of exposure in older buildings include firefighters, contractors, demolition workers, electricians, and plumbers.
The risk of asbestos-related diseases is highest for people who work directly with the raw mineral or with asbestos-containing products on a daily basis.
Some of the more frequent occurrences of asbestos exposure that cause mesothelioma include:
- Shipyard workers.
- Construction workers.
- Power plant workers.
- Chemical plant workers.
- Industrial workers.
- Boiler workers.
- Automotive mechanic.
Risk factors in construction and craft jobs
Construction workers and artisans are more likely to experience harmful exposures, especially when working in older homes and buildings constructed from contaminated materials.
Exposures can occur during a renovation, remodel, or demolition. If the asbestos insulation is disturbed, the fibers can become airborne and contaminate.
How does mesothelioma develop?
Long-term exposure to asbestos from a related cancer usually develops, but even minor exposures can be harmful.
Activities that disrupt asbestos-containing products release toxic fibers into the air.
Mesothelioma has a dose-response relationship to asbestos, which means that higher doses of asbestos exposure lead to an increased risk of developing mesothelioma.
When it comes to asbestos, high concentrations of fibers and long durations of exposure pose an increased risk of developing an asbestos-related disease.
Once inhaled, the body has a hard time getting rid of the sharp, sometimes irregular fibers, and they build up in the lungs or abdomen over time. Many years after the first exposure, these fibers can cause cancerous changes.
Cancer begins in the mesothelial cells, which comprise the protective membranes that cover the lungs, abdomen, and heart.
Possible theories for asbestos-related tumor development
The fibers inflame and irritate the mesothelial cells, leading to irreversible scarring, cell damage, and cancer.
The fibers enter the mesothelial cells and interrupt their life cycle. This can cause genetic changes that lead to cancer.
Asbestos causes the production of free radicals, which are molecules that damage DNA and cause healthy cells to undergo cancer-causing mutations.
Fibers can trigger the production of oncoproteins, which block genes that protect cells from uncontrolled growth and tumor formation.
The common ground of these theories: Asbestos causes damage that changes the natural life cycle of a cell.
Every healthy cell has genes that regulate growth and protect against cancer. Once asbestos blocks this function, cells can divide uncontrollably, causing malignant tumors to form locally and possibly metastasize, spreading throughout the body and forming metastatic tumors.
These tumors develop relatively late in the course of mesothelioma, but they can be the main source of symptoms for the patient.
While all types of asbestos cause mesothelioma, certain types, such as crocidolite and amosite, are more carcinogenic than others. Researchers believe that the varying chemical composition of different types of asbestos is what makes one type more carcinogenic than another.
The vast majority of people who work with asbestos will not develop a disease. Individual factors such as genetics play a role in the development of mesothelioma, while factors such as cigarette smoking play a role in the development of asbestos-related lung cancer.
The best way to prevent mesothelioma is to take a proactive stance about your health. If you believe that a previous job or home repair project exposed you to asbestos, you should request periodic medical exams for signs of asbestos-related illnesses.
If you or a loved one has a history of asbestos exposure, especially in the workplace, don’t wait for symptoms to appear. Instead, be proactive and consult your doctor.
Early detection offers the best opportunity for effective treatment.
Treatment options for mesothelioma include surgery, chemotherapy, radiation, and multimodal treatment. Surgery in patients with disease confined to the pleural space is reasonable.
The histopathologic classification of a patient’s malignant mesothelioma (ie, as epithelioid, sarcomatoid, or biphasic) plays a critical role in treatment decisions.
Patients whose mesotheliomas are sarcomatoid or biphasic (they have both epithelioid and sarcomatoid characteristics) have a worse prognosis and are generally not candidates for surgical intervention.
The results obtained with radiation therapy have been disappointing. Radiation has had no effect on survival, but has provided significant palliation in 50% of patients treated for chest pain and chest wall metastases.