Pleural mesothelioma is a rare and aggressive cancer that develops in the thin membrane lining the lungs and chest wall, almost always linked to past exposure to asbestos fibers that can take decades to trigger disease.
Understanding Pleural Mesothelioma
Pleural mesothelioma, also called malignant pleural mesothelioma, is a type of cancer that forms in the pleura, which is the thin tissue layer covering the lungs and lining the inside of the chest cavity. This protective membrane, called the mesothelium, normally allows the lungs to move smoothly during breathing. When cancer develops in this tissue, it is known as mesothelioma. The pleural form is the most common type, representing about 80% of all mesothelioma cases.[1]
This disease gets its name from the mesothelium tissue where it originates. The mesothelium is a specialized lining that protects and cushions various internal organs throughout the body. While mesothelioma can technically develop in any part of this lining, including around the abdomen, heart, or testicles, the vast majority of cases occur in the pleural tissue surrounding the lungs.[4]
Pleural mesothelioma is considered rare, with approximately 3,300 people diagnosed with all forms of mesothelioma each year in the United States. Of these cases, pleural mesothelioma accounts for roughly 80%. The disease affects men more frequently than women, and older veterans make up about 30% of all cases due to historical asbestos exposure in military settings.[1][7]
Epidemiology and Demographics
Mesothelioma remains a significant public health concern worldwide, particularly in countries with a history of heavy asbestos use. In the United States, the disease affects approximately 3,300 individuals annually, with pleural mesothelioma representing the largest proportion of these diagnoses. Australia has one of the highest rates of mesothelioma per capita globally, reflecting that country’s extensive asbestos mining and use throughout the twentieth century.[14]
The average age at diagnosis is around 60 years, though the disease can occur in younger or older individuals depending on when and how long they were exposed to asbestos. Men are affected significantly more often than women, primarily because occupational asbestos exposure historically occurred in male-dominated industries such as construction, shipbuilding, manufacturing, and mining. Most cases develop approximately 20 to 50 years after the initial asbestos exposure, which explains why many patients are in their sixties or seventies at the time of diagnosis.[7][1]
Since efforts to reduce and regulate asbestos exposure began in the United States during the 1970s and 1980s, there has been a decline in new mesothelioma cases since the year 2000. However, due to the long latency period between exposure and disease development, new cases continue to emerge from individuals exposed decades ago. In countries where asbestos is still mined or used, the incidence of pleural mesothelioma may continue to rise for years to come.[1]
Causes of Pleural Mesothelioma
Asbestos exposure is the primary cause of pleural mesothelioma, accounting for 70% or more of all diagnosed cases. Researchers believe the actual percentage may be even higher, as many patients may not remember or be aware of their exposure. Asbestos is a group of naturally occurring minerals that form long, thin, and extremely durable fibers. These fibers were once prized for their resistance to heat, fire, and chemicals, which led to widespread use in building materials, insulation, automotive parts, textiles, and many consumer products throughout much of the twentieth century.[1][4]
The danger arises when asbestos-containing materials are disturbed, cut, drilled, or damaged. This releases tiny asbestos fibers into the air, creating invisible particles small enough to be inhaled deep into the lungs. Once inside the respiratory system, these microscopic fibers travel to the outer edges of the lungs and become lodged in the pleura. The human body cannot break down or eliminate asbestos fibers because they are chemically and physically resistant to biological processes.[2]
Over many years, these trapped fibers cause repeated inflammation and irritation in the pleural tissue. This chronic inflammatory process disrupts normal cell function, damages cellular structures, activates genes that can promote cancer development, and generates harmful molecules called free radicals. These biological changes accumulate over decades, eventually leading to the development of cancerous cells in the pleural lining.[3]
It is important to note that intact, undisturbed asbestos materials do not pose an immediate health risk. The danger occurs only when the material is damaged or manipulated in ways that release the fibers into the air. This is why renovation or demolition of older buildings can be particularly hazardous if proper asbestos abatement procedures are not followed.[1]
Among different types of asbestos, amosite and crocidolite are most strongly associated with mesothelioma development. While asbestos is no longer mined in the United States, it is still imported from other countries for use in certain products, and it remains present in many older homes, schools, and commercial buildings.[3][4]
Other risk factors have been identified, though they are far less common than asbestos exposure. Some studies suggest that exposure to ionizing radiation, such as mantle radiation therapy used to treat Hodgkin lymphoma, may increase risk. Additionally, genetic factors may play a role, particularly mutations in a gene called BAP1 (BRCA1-associated protein 1), which has been linked to increased susceptibility to mesothelioma. It is important to note that smoking does not directly cause mesothelioma, although it significantly increases the risk of lung cancer in people who have also been exposed to asbestos.[3]
Risk Factors and High-Risk Groups
Understanding who is at greatest risk for developing pleural mesothelioma helps identify individuals who should be monitored more closely for symptoms. The primary risk factor is occupational asbestos exposure. Workers in certain industries had particularly high levels of contact with asbestos materials before regulations limiting its use took effect. These high-risk occupations include construction workers, shipyard workers, insulators, plumbers, pipefitters, electricians, mechanics, miners, and manufacturing workers in facilities that produced asbestos-containing products.[4]
Military veterans, especially those who served in the Navy, are at elevated risk. Asbestos was extensively used in military ships, vehicles, aircraft, and buildings from the 1930s through the 1970s. Navy personnel who worked in engine rooms, boiler rooms, or performed ship maintenance and repairs faced particularly high exposure levels. Veterans from all branches of the military may have been exposed through work in shipyards, on aircraft, in vehicles, or in base housing and barracks.[7]
Even people who never worked directly with asbestos can be at risk. Family members of workers can develop mesothelioma through what is called secondary or take-home exposure. This occurs when asbestos fibers are carried home on work clothing, shoes, hair, or skin, and are then inhaled by family members. This type of exposure has led to cases of mesothelioma in spouses and children of asbestos workers.[4]
Living near asbestos mines, processing facilities, or natural deposits of asbestos in the environment can also increase risk. Some communities built near these sites experienced higher rates of mesothelioma among residents who had no direct occupational exposure. Additionally, people who lived or worked in buildings where asbestos-containing materials were disturbed during renovation or deterioration may have been exposed.[4]
The duration and intensity of asbestos exposure matters. Generally, heavier and longer exposure increases the risk of developing mesothelioma. However, even relatively brief or low-level exposure can lead to disease in some individuals, particularly if they have genetic susceptibility factors. This unpredictability makes it important for anyone with any history of possible asbestos contact to inform their healthcare providers.[6]
Symptoms and Clinical Presentation
The symptoms of pleural mesothelioma typically develop slowly and may not appear until decades after asbestos exposure. The disease can take anywhere from 20 to 50 years to develop after initial exposure, which is called the latency period. Early symptoms are often vague and easily dismissed as signs of aging or less serious conditions, which is one reason why many people delay seeking medical care until the cancer is more advanced.[1][12]
The two main symptoms of pleural mesothelioma are persistent chest pain and shortness of breath. The chest pain often occurs under the rib cage or on one side of the chest. Shortness of breath typically worsens over time as the disease progresses. These symptoms occur because the cancer causes the pleura to thicken and can lead to fluid accumulation in the space between the lung and chest wall, a condition called pleural effusion. This fluid buildup and tissue thickening prevent the lungs from expanding normally during breathing.[1][5]
Other common symptoms include a persistent dry cough, hoarseness, or difficulty swallowing. Some patients notice lower back pain or pain that seems to radiate to other areas of the chest or abdomen. Physical changes can include swelling of the face and arms, though this is less common in early stages. Patients often experience unexplained weight loss, which occurs because the cancer affects metabolism and appetite. Fatigue is another frequent complaint, as the body expends energy fighting the disease and dealing with reduced oxygen levels from compromised lung function.[1][5]
Some people develop systemic symptoms such as fever, night sweats, or general feelings of unwellness. Lumps may be felt under the skin of the chest in some cases, though this typically indicates more advanced disease. Because many of these symptoms resemble other, more common respiratory conditions like pneumonia or bronchitis, pleural mesothelioma is often misdiagnosed initially, especially in patients whose doctors are unaware of their asbestos exposure history.[1][4]
Prevention Strategies
Since asbestos exposure is the overwhelming cause of pleural mesothelioma, prevention focuses primarily on avoiding contact with asbestos fibers. The most effective prevention strategy is to avoid occupational and environmental exposure to asbestos altogether. In workplaces where asbestos materials are present, strict safety protocols must be followed. This includes using proper protective equipment such as respirators and protective clothing, ensuring adequate ventilation, following proper handling procedures, and participating in training programs about asbestos safety.[4][7]
For people who work in construction, renovation, or demolition, it is essential to identify asbestos-containing materials before beginning work. Professional asbestos abatement specialists should be hired to safely remove or encapsulate asbestos rather than attempting to handle it without proper training and equipment. Homeowners living in older buildings should be aware that asbestos may be present in insulation, floor tiles, ceiling tiles, roofing materials, and other building components. These materials should not be disturbed without professional assessment and handling.[4]
Workers who have been exposed to asbestos should take steps to prevent secondary exposure to their families. This includes changing out of work clothes before leaving the workplace, showering before going home, and keeping work clothes separate from household laundry. These practices help prevent asbestos fibers from being carried into the home where family members could inhale them.[4]
For individuals who know they have been exposed to asbestos in the past, regular medical checkups are important. While there is no way to reverse past exposure, early detection of asbestos-related diseases can improve treatment outcomes. People with a history of asbestos exposure should inform all their healthcare providers about this history and discuss whether regular monitoring with chest x-rays or other imaging tests might be appropriate.[4]
How the Disease Develops: Pathophysiology
Understanding how pleural mesothelioma develops helps explain why it behaves the way it does and why it can be so difficult to treat. The disease process begins when asbestos fibers are inhaled and travel through the airways deep into the lungs. The smallest, most dangerous fibers can migrate all the way to the periphery of the lungs where they penetrate into the pleural space. Once embedded in the pleural tissue, these fibers cannot be removed by the body’s normal defense mechanisms.[2][3]
The presence of asbestos fibers in the pleura triggers a chronic inflammatory response. The body recognizes these foreign materials and attempts to eliminate them, but because asbestos fibers are so durable, the inflammatory process continues for years or decades without successfully removing the fibers. This persistent inflammation causes repeated cycles of tissue damage and repair in the pleural cells.[3]
Over time, this chronic irritation disrupts normal cellular processes. Cell division becomes abnormal, and genetic material within cells is damaged. The asbestos fibers can physically interfere with the machinery that controls how cells divide, causing errors during cell division. They also activate certain genes called proto-oncogenes that can promote cancer development when inappropriately activated. Additionally, the inflammatory process generates reactive oxygen species, also known as free radicals, which are highly reactive molecules that damage DNA, proteins, and other cellular components.[3]
These accumulated genetic and cellular changes eventually transform normal mesothelial cells into cancerous cells. The cancer cells multiply uncontrollably and form tumors in the pleural tissue. Unlike normal tissue, which grows in an organized manner and stops growing when appropriate, cancer cells ignore the body’s normal growth control signals. In pleural mesothelioma, the cancer typically forms a thick layer of tumor tissue that encases the lung and lines the inside of the chest wall.[10]
As the disease progresses, this tumor tissue causes the pleura to thicken significantly. The thickened, stiff pleura prevents the lung from expanding normally during breathing, which explains the shortness of breath that patients experience. The cancer also often causes fluid to accumulate in the pleural space, further compressing the lung and making breathing even more difficult. This fluid buildup occurs because the cancer disrupts the normal balance of fluid production and absorption in the pleural space.[9]
The cancer can spread locally by directly invading nearby structures such as the lung itself, the chest wall, the diaphragm (the muscle that separates the chest from the abdomen), or the pericardium (the sac around the heart). In more advanced stages, mesothelioma can spread through the lymphatic system to nearby lymph nodes, or it can spread through the bloodstream to distant organs, though this is less common than with some other types of cancer.[10]
There are three main cell types of pleural mesothelioma, classified based on how the cancer cells look under a microscope. Epithelioid mesothelioma is the most common type, accounting for 60% to 80% of cases. These cells are somewhat organized and tend to be the most responsive to treatment. Sarcomatoid mesothelioma is the rarest form, making up about 10% of cases. These cells look more disorganized and tend to grow and spread more aggressively, making them harder to treat. Biphasic mesothelioma contains a mixture of both epithelioid and sarcomatoid cells, accounting for 10% to 15% of cases. The behavior of biphasic mesothelioma depends on the proportion of each cell type present.[1][12]
