Pleural mesothelioma is a cancer that forms in the thin tissue lining the lungs and chest wall, known as the pleura. It is the most common type of mesothelioma, a rare cancer almost always linked to asbestos exposure. About 2,669 cases of mesothelioma were reported in the United States in 2022, and the disease typically appears decades after asbestos fibers are first inhaled.
How Pleural Mesothelioma Develops
The pleura is made up of two layers of specialized cells called mesothelial cells. One layer, the parietal pleura, lines the inside of the chest wall. The other, the visceral pleura, covers the surface of the lungs. A thin layer of fluid between them allows the lungs to expand and contract smoothly during breathing.
When asbestos fibers are inhaled, they can work their way into the pleura and become permanently lodged there. The body cannot dissolve or break down these fibers, so they cause repeated damage to the mesothelial surface over years and decades. Each round of damage triggers inflammation and tissue repair, and these cycles create a chemical environment that can eventually push normal cells toward cancer. Inflammatory signaling molecules involved in healing are also involved in tumor development, which is part of why chronic irritation from asbestos can lead to malignant transformation.
This process is slow. In a study of 312 confirmed cases, the time between initial asbestos exposure and diagnosis ranged from 14 to 72 years, with a median latency of 51 years. That means most people diagnosed today were exposed to asbestos in the 1960s, 70s, or 80s, often through occupations like construction, shipbuilding, insulation work, or manufacturing.
Primary Symptoms
Early symptoms of pleural mesothelioma are often mild and easy to mistake for other conditions. Chest pain and a painful cough are typically the first signs. Because the cancer grows along the pleural surface rather than forming a single mass, symptoms tend to develop gradually as more of the lining becomes affected.
As the disease progresses and the tumor spreads within the chest, it presses on surrounding structures. This can cause difficulty breathing, trouble swallowing, and pain from pressure on nerves or the spinal cord. One of the most common complications is pleural effusion, a buildup of fluid between the two layers of the pleura. This fluid compresses the nearby lung, making it increasingly hard to take a full breath. Pleural effusion is often what prompts a person to seek medical attention in the first place.
How It Is Diagnosed
A standard chest X-ray is usually the first test ordered when symptoms appear, but its findings are often nonspecific. CT scans are the primary imaging tool for evaluating pleural disease, offering much better detail for identifying abnormal thickening, masses, or fluid along the pleural surface. MRI and PET-CT scans provide additional information about how far the cancer has spread, its metabolic activity, and which nearby tissues may be involved. Ultrasound is particularly useful for detecting and measuring pleural fluid, and for guiding procedures like fluid drainage and needle biopsies.
Imaging alone cannot confirm mesothelioma. A tissue biopsy is required. If the scans show visible pleural masses, a needle biopsy guided by ultrasound or CT can be performed. When fluid keeps returning but scans don’t show an obvious mass, doctors may use video-assisted thoracoscopy (VATS), a minimally invasive procedure where a small camera is inserted into the chest. This allows the surgeon to see the entire pleural surface, take targeted tissue samples, and send them for microscopic analysis. The biopsy tissue undergoes both histological examination and immunohistochemical testing to distinguish mesothelioma from other cancers that can affect the pleura.
Stages of Pleural Mesothelioma
Pleural mesothelioma is staged using a system that evaluates how far the tumor has spread through the pleura, whether nearby lymph nodes are involved, and whether cancer has reached distant parts of the body.
- Stage I: The tumor is confined to the pleura on one side of the chest, with no lymph node involvement and no distant spread.
- Stage II: The tumor has grown into all pleural surfaces on the affected side, possibly extending into the diaphragm muscle or lung tissue, and may involve lymph nodes on the same side of the chest.
- Stage III: The cancer has invaded deeper structures such as the chest wall’s inner lining, the fat around the heart, or the outer surface of the pericardium. Lymph nodes on the opposite side of the chest or above the collarbone may be involved.
- Stage IV: The cancer has spread to distant organs, invaded the spine, ribs, heart muscle, or extended through the diaphragm into the abdomen.
Staging helps guide treatment decisions, though experts acknowledge the system can be imprecise for mesothelioma. The way this cancer grows along surfaces rather than forming discrete tumors makes it harder to assess with imaging alone compared to many other cancers.
Treatment Approaches
Treatment for pleural mesothelioma typically combines multiple approaches depending on the stage, the patient’s overall health, and whether the tumor can be surgically removed.
Surgery
Two main surgical options exist. Pleurectomy/decortication (P/D) is a lung-sparing surgery that removes the diseased pleural lining while leaving the lung intact. Extrapleural pneumonectomy (EPP) is more radical, removing the lung, the surrounding pleura, the diaphragm on the affected side, and the pericardium. EPP leaves fewer cancer cells behind but carries significantly higher risks, including greater surgical mortality, a more severe drop in heart and lung function, and a worse quality of life afterward. P/D is generally better tolerated and is the preferred option when it can adequately remove visible tumor. Patients with poor lung or heart function are only candidates for P/D. Those with cancer that has grown deep into the lung tissue may require EPP to achieve adequate tumor removal.
Immunotherapy
For patients whose tumors cannot be surgically removed, immunotherapy has become the standard first-line treatment. In 2020, the FDA approved a combination of two immune checkpoint inhibitors (nivolumab and ipilimumab) based on results from a major clinical trial involving 605 patients. The immunotherapy combination produced a median overall survival of 18.1 months compared to 14.1 months with traditional chemotherapy, a four-month advantage. Response rates were similar between the two groups (about 40%), but the survival benefit was meaningful enough to change the standard of care. Patients receive this combination for up to two years.
Chemotherapy
Before immunotherapy became available, the standard first-line treatment was a platinum-based chemotherapy drug combined with pemetrexed. This regimen remains an option, particularly for patients who are not good candidates for immunotherapy. Chemotherapy is also used alongside surgery in multimodal treatment plans, either before surgery to shrink the tumor or afterward to target remaining cancer cells.
Managing Fluid Buildup
Pleural effusion is one of the most distressing symptoms of pleural mesothelioma, and managing it is a central part of palliative care. Two main approaches exist for longer-term relief. Chemical pleurodesis involves injecting a substance (usually talc) into the pleural space to create inflammation that seals the two layers of the pleura together, preventing fluid from reaccumulating. The other option is an indwelling pleural catheter, a small tube placed in the chest that allows fluid to be drained at home on a regular basis. In practice, the catheter is far more commonly used. In one study, 94% of patients who underwent a definitive palliative procedure received a catheter rather than pleurodesis.
Prognosis and Survival
Pleural mesothelioma carries a poor prognosis overall. Even with the newer immunotherapy regimen, median survival for patients with unresectable disease is about 18 months. Patients who are candidates for surgery combined with other treatments generally do better, though outcomes vary widely based on the stage at diagnosis, the cell type of the tumor, and the patient’s fitness level.
One notable exception involves people who carry a mutation in the BAP1 gene. This inherited mutation increases the risk of developing mesothelioma but, paradoxically, is associated with a much better outcome. Patients with BAP1 mutations had a median survival of five years, compared to less than one year in a population-based control group. This is one of the clearest examples of how the biology of a specific tumor can dramatically influence how the disease behaves.