Pleural mesothelioma is a rare and aggressive cancer that develops in the thin tissue lining the lungs and chest wall, most commonly caused by inhaling asbestos fibers decades before symptoms appear.

Understanding Pleural Mesothelioma

Pleural mesothelioma is a cancer that forms in the pleura, which is the thin membrane covering the lungs and lining the inside of the chest cavity. The name comes from the mesothelium, a protective tissue layer that covers many internal organs. When cancer develops in this tissue, it’s called mesothelioma, and the pleural type is by far the most common form of this disease.^[1]

This condition stands out as particularly challenging because it usually takes many years, even decades, to develop after the initial exposure to harmful substances. Most people who receive this diagnosis were exposed to asbestos long ago, often without knowing they were putting their health at risk. The disease is uncommon but devastating, affecting the ability to breathe and causing significant discomfort as it progresses.^[2]

Pleural mesothelioma accounts for approximately 80 to 90 percent of all mesothelioma cases, making it the predominant form of this cancer. The disease affects the tissue surrounding the lungs rather than the lung tissue itself, which distinguishes it from lung cancer. This distinction is important because the two conditions require different approaches to treatment and have different patterns of progression.^[3]

How Common Is Pleural Mesothelioma

Mesothelioma is considered a rare disease overall, but pleural mesothelioma represents the vast majority of cases. In the United States, approximately 3,300 people receive a mesothelioma diagnosis each year, and about 80 percent of these cases are pleural mesothelioma.^[1]

The number of cases in the United States has been declining since around the year 2000. This decrease reflects the widespread efforts by government agencies and manufacturers to reduce asbestos exposure after scientists discovered the dangerous link between asbestos and mesothelioma in the 1960s and 1970s. However, because of the long delay between exposure and disease development, people who were exposed to asbestos decades ago continue to be diagnosed today.^[1]

Globally, mesothelioma remains a significant concern. The disease incidence increased during the late twentieth century, corresponding with the widespread use of asbestos in construction and manufacturing. While some regions have seen declining rates due to asbestos regulations, other parts of the world continue to experience rising numbers of cases as asbestos use persists.^[9]

The disease affects men more frequently than women, primarily because men were more likely to work in industries where asbestos exposure was common. Occupations such as construction, shipbuilding, manufacturing, and mining put workers at higher risk. The median age at diagnosis is 71 years, reflecting the long latency period between exposure and disease development.^[15]

What Causes Pleural Mesothelioma

Asbestos exposure is responsible for pleural mesothelioma in at least 70 percent of cases, though experts believe the actual percentage may be higher. Asbestos is a group of naturally occurring minerals that were once extensively used in building materials, insulation, automotive parts, and many other products because of their heat resistance and durability.^[1]

When materials containing asbestos are disturbed, they release tiny fibers into the air that are invisible to the naked eye. These fibers are so small and light that they can remain airborne for extended periods. When people inhale these particles, the fibers can travel deep into the lungs and settle in the pleura. Unlike most foreign substances, asbestos fibers are extremely durable and resistant to the body’s natural defense mechanisms, meaning they cannot be broken down or expelled.^[3]

Over many years, these trapped asbestos fibers cause repeated inflammation and scarring in the pleural tissue. This chronic irritation leads to cellular damage and changes that can eventually result in cancer. The process involves disruption of normal cell division, activation of certain genes that promote cancer growth, and generation of harmful molecules called free radicals that further damage cells.^[7]

While asbestos is the primary cause, other factors have also been linked to pleural mesothelioma in some cases. Exposure to ionizing radiation, such as that used in certain cancer treatments like mantle radiation therapy for Hodgkin lymphoma, has been associated with an increased risk. Additionally, genetic factors play a role in some families, with mutations in a gene called BAP1 increasing susceptibility to the disease.^[7]

It’s worth noting that smoking does not directly cause mesothelioma. However, people who both smoke and have been exposed to asbestos face a significantly higher risk of developing lung cancer compared to those who only have one of these risk factors. This demonstrates how different harmful exposures can work together to increase cancer risk.^[7]

Risk Factors for Developing Pleural Mesothelioma

Understanding risk factors helps identify who is most vulnerable to developing pleural mesothelioma and why prevention efforts are so important. The primary risk factor is occupational exposure to asbestos. Workers in certain industries faced particularly high exposure levels before safety regulations were implemented.^[3]

People who worked in construction, shipbuilding, automotive manufacturing, and asbestos mining or processing have elevated risk. Until the 1960s and 1970s, workers in these industries often handled asbestos materials without adequate protective equipment or ventilation. Shipyard workers, in particular, faced intense exposure because ships were heavily insulated with asbestos materials. Military veterans, especially those who served in the Navy, represent a significant portion of mesothelioma patients due to widespread asbestos use in military vessels and buildings.^[2]

Living with someone who worked with asbestos creates risk through what’s called secondary or paraoccupational exposure. Family members could be exposed when workers brought asbestos fibers home on their clothing, shoes, or skin. Washing the work clothes of someone who handled asbestos increases exposure risk. This type of exposure has affected many spouses and children of asbestos workers.^[8]

Living or working in buildings where asbestos-containing materials have been disturbed presents another risk scenario. Many older homes and buildings still contain asbestos in insulation, floor tiles, roofing materials, and other products. When these materials deteriorate or are disturbed during renovation or demolition without proper precautions, they can release dangerous fibers.^[3]

Geographic location matters as well. Living in areas with natural asbestos deposits or near asbestos mines or processing facilities increases exposure risk. Some regions have naturally occurring asbestos in the soil and rock, which can become airborne through natural weathering or human activities like farming or construction.^[3]

Time is a critical factor in mesothelioma risk. The disease typically develops 25 to 50 years after the initial asbestos exposure. This extraordinarily long latency period means that people who were exposed to asbestos in their youth or middle age may not develop symptoms until they are elderly. It also means that even though asbestos use has declined in many countries, new cases continue to emerge from past exposures.^[1]

Genetic predisposition plays a role in some families. Certain inherited mutations, particularly in the BAP1 gene, make individuals more susceptible to developing mesothelioma if they are exposed to asbestos. While having these genetic variants doesn’t guarantee someone will develop the disease, it does increase their vulnerability when combined with asbestos exposure.^[7]

Recognizing the Symptoms of Pleural Mesothelioma

The symptoms of pleural mesothelioma typically develop slowly and can easily be mistaken for less serious conditions. This is one reason why the disease is often diagnosed at advanced stages. Many people initially dismiss their symptoms as signs of aging, a respiratory infection, or other common ailments.^[1]

The two main symptoms that bring most patients to their doctor are ongoing chest pain and shortness of breath. The chest pain is often described as persistent discomfort that doesn’t go away and may worsen over time. It can occur anywhere in the chest but is frequently felt under the rib cage. Shortness of breath, medically called dyspnea, occurs because the cancer causes fluid to accumulate in the space between the lung and chest wall, putting pressure on the lung and making it difficult to breathe fully.^[1]

Many patients develop a persistent cough that won’t go away despite treatment for common causes like colds or bronchitis. The cough may be dry or produce small amounts of fluid. Some people also experience hoarseness or changes in their voice quality.^[1]

Difficulty swallowing, known as dysphagia, can occur when tumors grow large enough to press on the esophagus. This symptom typically appears as the disease progresses. Lower back pain may develop if the cancer spreads or if the accumulation of fluid in the chest affects posture and breathing mechanics.^[1]

Swelling of the face and arms can happen when tumors press on major blood vessels in the chest, restricting normal blood flow. This symptom, while less common, can be particularly distressing and is a sign that the disease has progressed significantly.^[1]

Unexplained weight loss is common in many cancers, including pleural mesothelioma. The body’s metabolism changes as cancer develops, and patients may lose their appetite or find that food doesn’t taste the same. This weight loss occurs without intentional dieting or changes in eating habits.^[4]

Night sweats, fatigue, and fever are systemic symptoms that reflect the body’s response to cancer. Fatigue in cancer patients is typically more profound than normal tiredness and doesn’t improve with rest. The fever is usually low-grade and intermittent rather than constant and high.^[1]

Some patients notice lumps or unusual thickening under the skin of their chest. These physical changes occur when tumors grow large enough to be felt through the chest wall. This symptom typically appears in more advanced stages of the disease.^[4]

Prevention Strategies

The most effective way to prevent pleural mesothelioma is to avoid exposure to asbestos. Since the 1980s, many countries have implemented strict regulations controlling asbestos use, and some have banned it entirely. In the United States, asbestos was significantly restricted starting in 1989, though it was not completely banned and some uses continue with strict controls.^[1]

For people who work in industries where asbestos exposure remains possible, following proper safety protocols is essential. This includes wearing appropriate protective equipment such as respirators, working in well-ventilated areas, using wet methods to prevent dust when cutting or handling materials that might contain asbestos, and following decontamination procedures before leaving work sites. Employers in these industries are required to provide safety training and protective equipment.^[3]

If you live in an older home built before the 1980s, it may contain asbestos in various materials. The key to safety is not disturbing these materials. If they are intact and in good condition, they generally don’t pose a risk. However, if you plan renovations or repairs that might disturb these materials, hire certified asbestos professionals to test for asbestos and, if necessary, remove it safely. Never attempt to remove asbestos materials yourself, as this can create dangerous exposure for you and your family.^[3]

For people who know they were exposed to asbestos in the past, regular medical checkups are important. While there’s no screening test that can detect mesothelioma before symptoms develop, staying vigilant about any respiratory symptoms and maintaining open communication with your doctor about your exposure history can help ensure early attention to any concerning symptoms. If you’re concerned about past exposure, discuss with your doctor whether regular checkups or specific monitoring might be appropriate for your situation.^[3]

Avoiding smoking is particularly important for people who have been exposed to asbestos. While smoking doesn’t directly cause mesothelioma, it significantly increases the risk of lung cancer in people with asbestos exposure. The combination of these two risk factors creates a much higher cancer risk than either factor alone.^[7]

How Pleural Mesothelioma Affects the Body

Understanding what happens in the body during pleural mesothelioma helps explain why the symptoms occur and why the disease is so difficult to treat. The pathophysiology involves multiple changes in normal bodily functions, starting with the initial damage from asbestos fibers and progressing through cancer development and spread.^[9]

When asbestos fibers reach the pleura, they trigger chronic inflammation. The body’s immune system recognizes these fibers as foreign invaders and attempts to eliminate them, but the fibers are too durable to be broken down. This leads to persistent inflammation that continues for years or decades. The ongoing inflammatory process creates an environment that promotes cellular damage and abnormal cell growth.^[7]

The inflammation and direct contact with asbestos fibers cause DNA damage in the cells of the pleura. This damage affects genes that normally control cell division and death. When these control mechanisms are disrupted, cells can begin to divide uncontrollably, which is the hallmark of cancer. The genomic landscape of mesothelioma is characterized mainly by alterations in tumor suppressor genes, which are genes that normally prevent cancer development. The most frequently affected genes include BAP1, CDKN2A, CDKN2B, MTAP, NF2, and TP53.^[9]

As cancer cells multiply, they form tumors in the pleura. Unlike some cancers that form distinct, removable masses, pleural mesothelioma often grows in a diffuse pattern, spreading along the surface of the pleura and encasing the lung in a thick layer of tumor tissue. This growth pattern makes complete surgical removal extremely challenging.^[9]

The growing tumors interfere with the normal function of the pleura. Normally, the pleura produces a small amount of fluid that allows the lung and chest wall to move smoothly against each other during breathing. In mesothelioma, the diseased pleura often produces excessive fluid, called a pleural effusion. This fluid accumulates in the space between the lung and chest wall, compressing the lung and making it difficult to breathe. This explains why shortness of breath and chest discomfort are such prominent symptoms.^[4]

As the disease progresses, the tumor can invade nearby structures. It may grow into the chest wall, causing pain as it affects nerves and other tissues. It can extend to the diaphragm, the large muscle that separates the chest from the abdomen and plays a crucial role in breathing. When the tumor affects the diaphragm, breathing becomes even more difficult.^[9]

In advanced stages, pleural mesothelioma can spread beyond the chest cavity. Cancer cells may travel through the lymphatic system to nearby lymph nodes and then to distant organs. Common sites of metastasis (cancer spread) include the opposite lung, the peritoneum (the lining of the abdomen), the liver, and even the brain and bones. When cancer spreads to distant sites, it becomes much more difficult to treat and significantly affects survival.^[9]

The systemic effects of pleural mesothelioma explain symptoms like weight loss, fatigue, and fever. Cancer cells alter normal metabolism and trigger inflammatory responses throughout the body. The body expends energy fighting the disease, and substances released by cancer cells can suppress appetite and cause muscle wasting. These systemic effects contribute significantly to declining health and quality of life as the disease progresses.^[15]