Mesothelioma is a rare, aggressive cancer that starts in the thin membrane lining several of your body’s internal organs. It develops most often in the tissue surrounding the lungs (called the pleura), though it can also form in the lining of the abdomen, heart, or testicles. The overwhelming majority of cases are linked to asbestos exposure, and the cancer is notorious for its long delay between exposure and diagnosis, with a median latency of about 34 years.
Where Mesothelioma Develops
Your body has a continuous layer of cells, called mesothelial cells, that forms a slick membrane around your lungs, abdominal organs, heart, and other structures. This lining helps organs move smoothly against each other. Mesothelioma can start anywhere along this membrane, but the location determines the type:
- Pleural mesothelioma forms in the lining around the lungs and is by far the most common type.
- Peritoneal mesothelioma develops in the abdominal lining and is the second most common.
- Pericardial mesothelioma starts in the sac surrounding the heart and is extremely rare.
Because pleural mesothelioma accounts for the vast majority of cases, most survival data and treatment research focuses on this form. The overall five-year survival rate for pleural mesothelioma across all stages is about 15%, based on patients diagnosed between 2015 and 2021 tracked by the American Cancer Society.
How Asbestos Causes Mesothelioma
Asbestos is a group of naturally occurring mineral fibers that were widely used in construction, insulation, shipbuilding, and manufacturing throughout the 20th century. When asbestos-containing materials are disturbed, microscopic fibers become airborne and can be inhaled or swallowed. Once lodged in the body’s mesothelial lining, these fibers are nearly impossible for the body to break down.
The damage unfolds through several biological processes that work together. Immune cells attempt to engulf and digest the fibers but fail because the fibers are too long and durable. These “frustrated” immune cells produce large quantities of harmful molecules called free radicals, particularly when the asbestos fibers contain iron. This triggers chronic inflammation, which is a well-established driver of cancer development. At the same time, asbestos fibers can physically enter cells, reaching both the main body of the cell and the nucleus where DNA is stored. During cell division, the fibers can tangle with chromosomes, directly damaging genetic material. A third mechanism involves the fibers acting like magnets for carcinogenic chemicals already in the body, concentrating them in the tissue where the fibers are lodged.
This combination of chronic inflammation, direct genetic damage, and chemical concentration explains why mesothelioma is so strongly tied to asbestos and why it takes so long to appear. The median time from first asbestos exposure to diagnosis is about 34 years, with a range that spans from under 10 years to more than 80 years in some cases. Most people develop the disease at least 14 years after exposure, and some don’t receive a diagnosis until nearly 60 years later.
Who Is Most at Risk
Occupational asbestos exposure remains the primary risk factor. An analysis of U.S. mesothelioma patients diagnosed between 2006 and 2022 identified the industries with the highest case counts, looking specifically at jobs held at least 20 years before diagnosis to account for the disease’s long latency. Manufacturing topped the list, particularly in metals, transportation equipment, and chemicals. Retail trade (especially motor vehicle and parts dealers), construction, military service (with U.S. Navy personnel making up two-thirds of military cases), and utilities rounded out the top five.
Navy veterans face elevated risk because asbestos was heavily used in ship construction for insulation, fireproofing, and pipe lagging. Construction workers, plumbers, electricians, and industrial tradespeople who worked with older buildings are also disproportionately affected. Secondary exposure is possible too: family members of asbestos workers have developed mesothelioma from fibers carried home on clothing.
Symptoms by Type
Mesothelioma symptoms vary depending on where the cancer develops, and they often mimic more common conditions, which contributes to late diagnosis.
Pleural mesothelioma typically causes shortness of breath as fluid builds up between the lung and chest wall. Chest wall pain and unexplained weight loss are also common. Because these symptoms overlap with pneumonia, heart failure, or other lung diseases, the cancer is often not suspected initially.
Peritoneal mesothelioma presents differently. Abdominal pain, nausea, vomiting, and fluid buildup in the abdomen are the hallmark symptoms, along with more rapid weight loss than the pleural form. A physical exam may reveal a solid mass in the abdomen.
How Mesothelioma Is Diagnosed
Diagnosis typically starts with imaging. CT scans are considered the standard first-line study for evaluating suspected mesothelioma because they are widely available and cost-effective. MRI offers advantages in specific situations: it is better at detecting whether the tumor has invaded the diaphragm muscle or the chest wall, which matters for surgical planning. For most other staging features, CT and MRI perform comparably.
Imaging alone cannot confirm mesothelioma. A tissue biopsy is required. This usually involves a surgical procedure rather than a simple needle biopsy, because pathologists need a sufficient tissue sample to distinguish mesothelioma from other cancers that can spread to the same areas. The biopsy results, combined with imaging, determine the stage of the disease.
Staging and What It Means for Prognosis
Pleural mesothelioma is staged using a system that evaluates three factors: how far the primary tumor has spread (T), whether nearby lymph nodes are involved (N), and whether the cancer has reached distant sites in the body (M). These combine into four stages:
- Stage I: The tumor is confined to the pleural lining on one side, with no lymph node involvement or distant spread.
- Stage II: The tumor may have grown into nearby structures like the lung or diaphragm, with limited lymph node involvement.
- Stage III: More extensive local spread with involvement of lymph nodes farther from the original tumor site.
- Stage IV: The cancer has spread to distant organs.
Five-year survival rates reflect these stages clearly. When mesothelioma is still localized, the five-year relative survival rate is 23%. For regional disease (spread to nearby structures or lymph nodes), it drops to 15%. Once it has spread to distant sites, the rate is 11%. These numbers represent averages across many patients and don’t predict individual outcomes, but they illustrate how much earlier detection matters.
Treatment Options
Treatment for mesothelioma depends on the stage at diagnosis, the location of the cancer, and the patient’s overall health. The three main approaches are surgery, chemotherapy, and immunotherapy, often used in combination.
For patients whose tumors can be surgically removed, the goal is to take out as much cancer as possible. This may involve removing the affected pleural lining, or in more extensive cases, removing the lung along with the surrounding membrane. Surgery is most commonly considered for earlier-stage disease.
For patients with unresectable pleural mesothelioma (tumors that cannot be fully removed surgically), the treatment landscape shifted significantly in 2020. The FDA approved a combination immunotherapy regimen as a first-line treatment after a clinical trial of over 600 patients showed it improved median overall survival to 18.1 months, compared to 14.1 months with standard chemotherapy. Notably, while the initial tumor response rates were similar between immunotherapy and chemotherapy (around 40%), the responses to immunotherapy lasted considerably longer, with a median duration of 11 months versus 6.7 months for chemotherapy.
Chemotherapy, typically a platinum-based drug combined with another agent, remains an option and is still used when immunotherapy isn’t appropriate or as part of a multimodal approach. Some treatment plans combine surgery with chemotherapy or radiation to address any remaining cancer cells after an operation.
Side effects of immunotherapy tend to differ from chemotherapy. The most common issues reported in clinical trials include fatigue, muscle and joint pain, skin rash, diarrhea, shortness of breath, nausea, and decreased appetite. Because immunotherapy works by activating the immune system, it can sometimes cause the immune system to attack healthy tissue, which requires careful monitoring throughout treatment.
Why Early Detection Is Difficult
Mesothelioma’s decades-long latency period creates a fundamental challenge. Someone exposed to asbestos in their 20s or 30s may not develop symptoms until their 60s or 70s, long after the exposure is forgotten. The early symptoms, particularly shortness of breath and chest pain, are common enough that they’re frequently attributed to aging, heart disease, or other lung conditions before mesothelioma enters the picture. There is currently no widely recommended screening test for the general population, though people with known asbestos exposure histories are sometimes monitored with periodic imaging.