Mesothelioma is a cancer that develops in the thin tissue lining certain organs, most commonly the lungs. It is strongly linked to asbestos exposure, often appearing 20 to 40 years after the initial contact with asbestos fibers. About 63,600 cases were diagnosed in the United States between 2003 and 2022, and the disease carries a five-year survival rate of roughly 15% across all stages.
Where Mesothelioma Develops
The cancer originates in mesothelial cells, which form the protective lining around several organs. The location determines the type:
- Pleural mesothelioma grows in the tissue surrounding the lungs. This is by far the most common form, accounting for 81% of all cases.
- Peritoneal mesothelioma forms in the lining of the abdomen. It makes up about 11% of cases and is notably more common in women, representing roughly 20% of female mesothelioma diagnoses compared to 8% in men.
- Pericardial mesothelioma develops around the heart. It is extremely rare, representing just 0.2% of cases.
- Tunica vaginalis mesothelioma affects the tissue surrounding the testicles. Also 0.2% of cases, it occurs only in men.
How Asbestos Causes Mesothelioma
Asbestos fibers are microscopic, sharp, and remarkably durable. When inhaled or swallowed, they can lodge in the mesothelial lining and stay there permanently. Three properties determine how dangerous a given fiber is: its dimensions, its durability, and the dose a person received.
Long, thin fibers (longer than 10 to 20 micrometers) are the most harmful because immune cells called macrophages cannot fully engulf them. The macrophages try repeatedly and fail, a process known as frustrated phagocytosis. Each failed attempt releases a burst of free radicals, highly reactive molecules that damage nearby DNA. Over years and decades, this chronic inflammation and genetic damage accumulate until cells begin dividing uncontrollably.
The latency period between first exposure and diagnosis typically ranges from 20 to 40 years, though cases have appeared as early as 10 years after exposure and as late as 71 years. Research shows that the risk of developing pleural mesothelioma continues to increase even beyond 40 years from the last exposure. This is why new cases keep appearing today, decades after many countries restricted asbestos use.
Who Is Most at Risk
Occupational asbestos exposure is the dominant risk factor. Construction workers represent the largest currently exposed group in the United States, with an estimated 1.3 million workers at some level of risk. Historically, the heaviest exposure hit pipe fitters, shipyard workers, military personnel (especially U.S. Navy), automobile mechanics, and insulation installers.
The list of affected occupations is long: boilermakers, electricians, plumbers, roofers, welders, sheet metal workers, demolition crews, refinery workers, and railroad employees, among many others. Industries with the highest historical exposure include asbestos product manufacturing, shipbuilding, power plants, oil refineries, and automotive brake repair shops.
Men are diagnosed about three times more often than women, largely reflecting the gender makeup of these industries. However, secondary exposure also occurs. Family members of asbestos workers have developed mesothelioma from fibers carried home on clothing. Women with peritoneal mesothelioma sometimes have no identifiable asbestos exposure, and researchers are still investigating other possible causes.
Symptoms and How They Progress
Mesothelioma is notoriously difficult to catch early because its symptoms overlap with many common, less serious conditions. In pleural mesothelioma, the two hallmark symptoms are persistent chest pain and shortness of breath. These can easily be mistaken for a respiratory infection, heart disease, or even aging.
Other symptoms include a persistent cough, hoarseness, difficulty swallowing, lower back pain, swollen face and arms, unexplained weight loss, night sweats, fatigue, and fever. In early stages (stage 1), the cancer is confined to the pleural lining and may produce only mild discomfort. By stage 4, it has spread to distant organs, commonly the bones, liver, diaphragm, heart, or central nervous system, and symptoms become significantly more severe and varied.
Peritoneal mesothelioma presents differently, with abdominal swelling, pain, nausea, and changes in bowel habits. Because these symptoms are vague, diagnosis is often delayed regardless of type.
How Mesothelioma Is Diagnosed
Imaging scans, typically a CT scan or MRI, are usually the first step when symptoms raise suspicion. But a definitive diagnosis requires a tissue biopsy. Pathologists examine the sample under a microscope and run a panel of specialized staining tests to distinguish mesothelioma from lung cancer and other cancers that can look similar.
This distinction matters because mesothelioma cells and lung cancer cells can appear nearly identical. The staining panel checks for proteins that are present in mesothelioma but absent or rare in lung cancer, and vice versa. One particularly useful marker is a protein called BAP1: when it’s missing from the cells, it’s highly specific to mesothelioma and is found in only about 1% of lung cancers.
There is one FDA-approved blood test for mesothelioma, called MESOMARK, which measures a protein fragment shed by mesothelioma cells. It performs best at distinguishing mesothelioma from benign conditions, with accuracy declining when compared against other cancers. Other blood markers are under investigation, including fibulin-3, which showed promising early results with up to 95% sensitivity and specificity in initial studies. However, follow-up research has produced mixed results. Blood tests currently serve as supplementary tools rather than standalone screening methods, and none are reliable enough to use for routine screening in asbestos-exposed populations.
Survival Rates by Stage
Mesothelioma survival depends heavily on how far the cancer has spread at diagnosis. Based on data from 2015 to 2021 collected by the American Cancer Society:
- Localized (cancer confined to its origin): 23% five-year survival rate
- Regional (spread to nearby structures or lymph nodes): 15% five-year survival rate
- Distant (spread to remote organs): 11% five-year survival rate
The combined five-year survival rate across all stages is 15%. These numbers reflect averages and don’t account for individual factors like cell type, age, or overall health. Peritoneal mesothelioma, when treated aggressively, sometimes carries a somewhat better prognosis than pleural mesothelioma.
Treatment Options
Treatment for mesothelioma has shifted significantly in recent years. Immunotherapy, which helps the immune system recognize and attack cancer cells, is now a first-line option alongside or instead of traditional chemotherapy.
For newly diagnosed pleural mesothelioma, current guidelines from the American Society of Clinical Oncology recommend a combination of two immunotherapy drugs as a primary treatment. This recommendation followed a major clinical trial showing marked improvement in overall survival, particularly for patients with the more aggressive, non-epithelioid cell types. For patients with the more common epithelioid cell type, either immunotherapy or chemotherapy (a platinum-based drug combined with another agent) is considered reasonable, and the choice depends on the patient’s overall health, other medical conditions, and treatment preferences.
A third approach combines chemotherapy with immunotherapy, which may be offered to patients regardless of cell type. Surgery is an option for some patients with early-stage disease, with the goal of removing as much visible cancer as possible. This is most feasible when the cancer is still confined to the pleural lining (stage 1). Radiation therapy may be used after surgery or to help control symptoms in more advanced disease.
Because mesothelioma is typically diagnosed at a later stage, treatment often focuses on controlling the disease and maintaining quality of life rather than achieving a cure. Draining fluid that builds up around the lungs (a common complication called pleural effusion) can significantly relieve breathing difficulty. Pain management and supportive care play central roles throughout treatment.