Malignant mesothelioma is a rare and aggressive cancer that develops in the thin tissue lining the body’s internal organs, most commonly the lungs. This disease is strongly linked to asbestos exposure and often takes decades to appear after contact with this harmful mineral. Understanding mesothelioma, its causes, and available support options can help patients and families navigate this challenging diagnosis.
Epidemiology
Malignant mesothelioma is considered a rare cancer, with approximately 2,000 to 3,300 new cases diagnosed in the United States each year[1][2]. The disease affects men much more frequently than women, largely because men have historically been more likely to work in industries where asbestos exposure occurred[1][8]. Most people diagnosed with mesothelioma are over 65 years old, with the median age of diagnosis being 71 years[15].
The prevalence of this cancer varies by geographic region and occupation. In the United States, veterans account for one in three mesothelioma patients, reflecting the widespread use of asbestos in military settings, particularly in shipbuilding and naval vessels[3]. The disease shows a long latency period, meaning symptoms typically appear 10 to 50 years after the initial asbestos exposure[2][3].
Mesothelioma cases have been declining in developed countries since around 2000, thanks to stricter regulations limiting asbestos use and better workplace safety measures[12][15]. However, the global incidence is expected to increase in countries where asbestos use has not been fully banned or regulated[15].
Causes
Asbestos exposure is the primary cause of malignant mesothelioma, accounting for 70 to 80 percent of all cases[2][12]. Asbestos is a group of naturally occurring minerals that form long, thin, very strong fibers resistant to heat, fire, and chemicals[3]. During the 20th century, asbestos was widely used in construction, shipbuilding, insulation, automotive parts, and many consumer products before scientists discovered its serious health dangers[3][8].
When materials containing asbestos are disturbed, tiny asbestos fibers become airborne. These fibers are so small they cannot be seen with the naked eye. People who breathe in or swallow these fibers can develop mesothelioma decades later[3]. The fibers are too tough for the body to break down, so they remain in the tissue, causing long-term inflammation and scarring. Over time, this damage can lead to changes in cells that result in cancer[2][12].
Among the different types of asbestos, amosite and crocidolite are most strongly associated with mesothelioma development[4]. While asbestos is the main cause, other factors have been linked to the disease. Exposure to ionizing radiation, such as mantle radiation therapy used to treat Hodgkin lymphoma, can increase risk[2][4]. Additionally, exposure to erionite, an asbestos-like mineral once used in road construction, has been connected to mesothelioma[2].
Genetic factors also play a role in some cases. Inherited mutations in the BAP1 gene can make individuals more susceptible to developing certain cancers, including mesothelioma[2][4]. However, it is important to note that not everyone exposed to asbestos develops mesothelioma, and some people diagnosed with the disease have no known history of asbestos exposure[2][3].
Risk Factors
Certain groups of people face a higher risk of developing malignant mesothelioma based on their occupation, living situation, and personal characteristics. Workers in specific industries have been most heavily exposed to asbestos over the years. These at-risk occupations include construction and building demolition, shipbuilding, mining, milling, military service, and auto repair[2][3].
Living with someone who works with asbestos also increases risk, a phenomenon known as secondary or take-home exposure[5][8]. Family members of asbestos workers can be exposed when asbestos fibers are carried home on work clothes, shoes, or skin. Living or working in buildings where asbestos-containing materials have been disturbed presents another risk[3]. Many older homes and public buildings, including some schools, contain asbestos in their insulation and construction materials[8].
The risk is generally low if asbestos remains contained within building materials, but it increases significantly when materials begin to deteriorate or during remodeling and demolition activities[8]. People living in areas with natural asbestos deposits or near asbestos mines or factories also face elevated risk[3]. Biological sex is another risk factor, with males developing mesothelioma more frequently than females[2][12].
Previous radiation exposure, particularly radiation treatments to the chest area for cancer, increases the likelihood of developing mesothelioma[2]. Individuals with inherited changes in the BAP1 gene have a genetic predisposition to certain cancers, including mesothelioma[2]. The amount and duration of asbestos exposure matter greatly—the more asbestos a person is exposed to and the longer the exposure period, the higher the risk[8].
Symptoms
Symptoms of malignant mesothelioma develop slowly and often do not appear until decades after asbestos exposure. The specific symptoms depend on where in the body the cancer develops. Because symptoms can be vague and similar to other, more common conditions, mesothelioma is frequently misdiagnosed initially, which can delay proper treatment[2][9].
Pleural mesothelioma, which affects the tissue around the lungs, is the most common type and causes respiratory symptoms[1][2]. Patients typically experience chest pain, often felt under the rib cage, and painful coughing. Shortness of breath, known medically as dyspnea, becomes progressively worse as the disease advances. This occurs because the cancer causes the pleura to thicken, preventing the lungs and chest from expanding normally[9]. Lumps may appear under the skin on the chest, and patients often feel persistent tiredness and experience unexplained weight loss[1][2].
Peritoneal mesothelioma affects the tissue lining the abdomen and presents different symptoms[1][2]. Patients notice abdominal pain and swelling as fluid accumulates in the belly. Nausea and digestive problems are common, along with loss of appetite. Like pleural mesothelioma, peritoneal mesothelioma causes fatigue and weight loss that cannot be explained by other factors[2][5].
Additional symptoms that can occur with mesothelioma include fever, night sweats, difficulty swallowing, hoarseness, and lower back pain[2][12]. Some patients develop problems with blood clotting when clots form inappropriately[5]. Rare forms of mesothelioma affecting the heart can cause trouble breathing and chest pains, while mesothelioma around the testicles may first appear as swelling or a mass[1][2].
The symptoms of mesothelioma can be bothersome but are easy to dismiss or attribute to other conditions like the flu, pneumonia, or gastrointestinal issues. Many people delay seeing their healthcare provider until their cancer is more advanced, which significantly affects treatment options and outcomes[12]. Anyone with a history of asbestos exposure who develops persistent symptoms should inform their doctor about their exposure history[3].
Prevention
There is no guaranteed way to prevent malignant mesothelioma, but reducing or avoiding asbestos exposure can significantly lower risk[27]. For people who work in industries where asbestos exposure is possible, following all safety precautions is essential. This includes wearing protective clothing and using respirators or other breathing protection devices[5]. Employers in these industries should provide proper safety equipment and training to all workers.
If you think your home might contain asbestos, do not attempt to inspect or remove it yourself. Many older homes built before the 1980s used asbestos in insulation, floor tiles, roofing materials, and other construction components[8]. Hire a trained asbestos expert to assess your home and, if necessary, safely remove asbestos-containing materials[5][8]. Disturbing asbestos without proper precautions can release dangerous fibers into the air.
For individuals with a history of asbestos exposure, regular medical checkups and screenings can help detect problems early. While there is no standard screening test specifically for mesothelioma, people who know they have been exposed to asbestos should discuss their risk with their doctor[3]. Being aware of potential symptoms and reporting them promptly can lead to earlier diagnosis, which is one of the most important factors in improving outcomes for mesothelioma patients.
Education about asbestos exposure is crucial for prevention. Workers in at-risk occupations should understand the dangers of asbestos and recognize situations where they might be exposed. Family members of these workers should also be aware of secondary exposure risks and take steps to prevent asbestos fibers from being brought into the home, such as changing work clothes before leaving the workplace[8].
Pathophysiology
Malignant mesothelioma begins when cells in the mesothelium—a thin layer of tissue that covers and protects internal organs—undergo abnormal changes. The mesothelium serves important functions in the body. It produces a lubricating fluid that allows organs to move smoothly against each other during activities like breathing and digestion[8][27].
When asbestos fibers enter the body through breathing or swallowing, they travel to the mesothelium and become lodged in the tissue. Because these fibers are extremely durable and resistant to breakdown by the body’s natural processes, they remain in place for decades[3][12]. The presence of these fibers causes repeated inflammation in the surrounding tissue. Over time, this chronic inflammation leads to scarring and cellular damage.
The asbestos fibers disrupt normal cellular processes in multiple ways. They interfere with cell division, causing cells to divide incorrectly. They activate certain genes called proto-oncogenes that can promote cancer development when they malfunction[4]. The fibers also trigger the production of harmful molecules called free radicals, which damage cellular components including DNA. These cumulative changes eventually cause cells to transform from normal to cancerous.
Unlike many other cancers that grow as distinct tumors, mesothelioma often develops as multiple small tumors that can merge together to form a sheet-like layer over the affected organs[2]. This growth pattern makes mesothelioma particularly difficult to treat surgically because it spreads along the thin tissue rather than forming a single mass that can be easily removed.
As mesothelioma progresses, the cancerous tissue thickens and may cause fluid to accumulate in body cavities. In pleural mesothelioma, fluid builds up between the layers of the pleura, compressing the lung and making breathing difficult[9]. In peritoneal mesothelioma, fluid collects in the abdominal cavity, causing swelling and pain. Eventually, the cancer can invade nearby tissues and organs and spread to distant parts of the body through the lymphatic system or bloodstream, a process called metastasis[2][14].