Mesothelioma

Mesothelioma is a rare, aggressive cancer that arises in the mesothelium — the thin membrane lining the lungs, abdomen, heart, and testes. Approximately 3,000 new cases are diagnosed in the United States each year, and asbestos exposure is the established cause in roughly 80% of cases.¹

The mesothelium consists of two layers: a visceral layer that covers the organ surface and a parietal layer that lines the body cavity. Between these layers, a small amount of lubricating fluid allows organs to move smoothly during breathing and digestion. When asbestos fibers become embedded in this tissue, they cause chronic inflammation and DNA damage that can trigger malignant transformation over a period of decades.²

Because of its long latency period — typically 20 to 50 years between first exposure and diagnosis — mesothelioma disproportionately affects older adults, with the median age at diagnosis being 72 years. The disease is roughly four times more common in men than women, reflecting historical occupational exposure patterns in construction, shipbuilding, and industrial trades.¹

Mesothelioma is classified by the anatomical site where it develops: pleural (lungs), peritoneal (abdomen), pericardial (heart), and testicular (tunica vaginalis). It is also classified by cell type — epithelioid, sarcomatoid, or biphasic — which significantly affects prognosis and treatment selection.²

Mesothelioma is categorized by the location in the body where the tumor originates. Each type has distinct symptoms, treatment approaches, and survival outcomes.

• Pleural mesothelioma accounts for approximately 80% of all diagnoses and develops in the pleural lining surrounding the lungs. It is the most studied type, with the most established treatment protocols including surgery, chemotherapy, and immunotherapy.¹
• Peritoneal mesothelioma represents 15–20% of cases and forms in the peritoneal lining of the abdominal cavity. When treated with cytoreductive surgery and heated intraperitoneal chemotherapy (HIPEC), peritoneal mesothelioma has a better prognosis than the pleural type, with 5-year survival rates exceeding 50% at specialized centers.³
• Pericardial mesothelioma accounts for fewer than 1% of cases and develops in the pericardial sac around the heart. It is frequently diagnosed postmortem due to nonspecific cardiac symptoms and limited diagnostic access to the pericardium.²
• Testicular mesothelioma (tunica vaginalis) is the rarest form, with fewer than 100 documented cases in medical literature. It typically presents as a painless scrotal mass and has a somewhat better prognosis than other types when treated with orchiectomy and adjuvant therapy.²

Within each anatomical type, the tumor's cell type (histology) plays a critical role in treatment response:

• Epithelioid — the most common (60–70% of cases) and most responsive to treatment, with the best overall survival.⁴
• Sarcomatoid — the least common (10–20%) and most aggressive, with limited response to standard chemotherapy.⁴
• Biphasic — a mixture of epithelioid and sarcomatoid cells (20–30%), with prognosis depending on the ratio of each cell type present.⁴

Mesothelioma symptoms vary by type and often mimic those of more common respiratory or gastrointestinal conditions, which contributes to frequent misdiagnosis and delayed treatment. Symptoms typically do not appear until the disease has reached an advanced stage.¹

Pleural mesothelioma symptoms:

• Persistent chest pain or tightness, often on one side
• Shortness of breath (dyspnea), initially with exertion and progressing to rest
• Pleural effusion — fluid accumulation between the lung and chest wall
• Chronic dry cough that does not respond to standard treatments
• Unexplained weight loss (more than 10% of body weight over 6 months)
• Fatigue and general malaise
• Difficulty swallowing (dysphagia) in advanced cases
• Night sweats and low-grade fever

Peritoneal mesothelioma symptoms:

• Abdominal pain or swelling
• Ascites — fluid accumulation in the abdominal cavity
• Nausea, vomiting, or changes in bowel habits
• Unexplained weight loss despite abdominal distension
• Loss of appetite (anorexia)
• Palpable abdominal mass in advanced disease

Pericardial mesothelioma symptoms:

• Chest pain that worsens when lying down
• Heart palpitations or irregular heartbeat (arrhythmia)
• Shortness of breath, especially when lying flat (orthopnea)
• Pericardial effusion — fluid around the heart
• Signs of cardiac tamponade in acute presentations

Because these symptoms overlap with common conditions such as pneumonia, COPD, irritable bowel syndrome, and congestive heart failure, patients should inform their physician of any history of asbestos exposure. A detailed occupational and environmental history is critical for prompting the specialized imaging and biopsy procedures necessary for accurate diagnosis.⁵

Asbestos exposure is the primary established cause of mesothelioma, responsible for approximately 80% of all cases.¹ Asbestos is a group of naturally occurring silicate minerals composed of thin, durable fibers that were widely used in construction, insulation, shipbuilding, automotive manufacturing, and dozens of other industries throughout the 20th century.

When asbestos-containing materials are disturbed — during cutting, drilling, demolition, or natural deterioration — microscopic fibers become airborne. Once inhaled or ingested, these fibers can penetrate deep into the body and become permanently lodged in the mesothelial tissue. The body cannot break down or expel asbestos fibers, so they persist indefinitely, causing ongoing cellular irritation.⁶

The mechanism of asbestos-induced carcinogenesis involves multiple pathways:

• Chronic inflammation — Embedded fibers trigger a sustained inflammatory response, releasing reactive oxygen species (ROS) that damage DNA over decades.²
• Direct genotoxicity — Asbestos fibers can physically interfere with cell division by tangling with chromosomes during mitosis, leading to chromosomal abnormalities.⁶
• Tumor suppressor gene inactivation — Asbestos exposure is associated with loss of the BAP1, NF2, and CDKN2A tumor suppressor genes, which normally prevent uncontrolled cell growth.⁴
• Fiber translocation — Inhaled fibers migrate from the lungs to the pleural space via lymphatic drainage, while ingested fibers penetrate the intestinal wall to reach the peritoneum.⁶

All six regulated types of asbestos — chrysotile, amosite, crocidolite, tremolite, anthophyllite, and actinolite — are classified as Group 1 carcinogens (confirmed human carcinogens) by the International Agency for Research on Cancer (IARC). There is no safe level of asbestos exposure.⁶

In a small percentage of cases, mesothelioma occurs without a clear history of asbestos exposure. Possible contributing factors in these cases include exposure to erionite (a naturally occurring zeolite mineral), radiation therapy to the chest or abdomen, and germline BAP1 mutations that create a hereditary predisposition to mesothelioma and other cancers.⁴

While asbestos exposure is the dominant risk factor for mesothelioma, several additional factors influence an individual's likelihood of developing the disease:¹

• Occupational asbestos exposure — Workers in construction, shipbuilding, power plants, refineries, steel mills, automotive repair (brake/clutch work), and insulation installation faced the highest exposure levels. Military service, particularly in the Navy, is a significant source of occupational exposure.⁶
• Duration and intensity of exposure — Higher cumulative doses of asbestos increase the risk, though even brief, high-intensity exposures have been linked to mesothelioma.²
• Fiber type — Amphibole fibers (amosite, crocidolite) are more potent carcinogens for mesothelioma than chrysotile (serpentine), though all types cause cancer.⁶
• Secondary (para-occupational) exposure — Family members of asbestos workers developed mesothelioma from fibers carried home on clothing, hair, and skin. This is sometimes called "take-home" or "bystander" exposure.⁶
• Environmental exposure — Residents near asbestos mines, processing facilities, or naturally occurring asbestos deposits face elevated risk. The Libby, Montana vermiculite mine contamination is a well-documented example.⁷
• Age and sex — Mesothelioma is most commonly diagnosed in men over 65, reflecting historical patterns of male-dominated industrial occupations with heavy asbestos use.¹
• Genetic susceptibility — Germline mutations in the BAP1 gene are associated with a hereditary cancer predisposition syndrome that includes increased risk of mesothelioma, uveal melanoma, and renal cell carcinoma.⁴
• Radiation exposure — Prior radiation therapy to the chest or abdomen has been associated with mesothelioma in a small number of cases, with a latency period of 10–20 years.²
• SV40 virus — Simian virus 40, which contaminated some polio vaccines administered between 1955 and 1963, was initially suspected as a co-carcinogen. Subsequent research has not confirmed a causal link with mesothelioma.²

Notably, smoking does not cause mesothelioma. Unlike asbestos-related lung cancer, where smoking and asbestos exposure have a synergistic effect, smoking has no established role in mesothelioma development. However, smoking does worsen overall lung function and can complicate treatment.¹

Diagnosing mesothelioma is a multi-step process that typically begins when a patient presents with persistent respiratory or abdominal symptoms, particularly if there is a known history of asbestos exposure. Because symptoms mimic common conditions, the median time from symptom onset to diagnosis is 3–6 months.⁵

Step 1: Clinical evaluation and imaging

The diagnostic workup begins with a thorough medical history (including occupational and environmental exposure history), physical examination, and initial imaging:

• Chest X-ray — Often the first imaging study, which may show pleural effusion, pleural thickening, or a mass. However, chest X-rays lack the sensitivity to detect early-stage disease.⁵
• CT scan (computed tomography) — The primary imaging tool for mesothelioma. Contrast-enhanced CT of the chest and abdomen provides detailed views of pleural thickening, nodularity, effusions, and potential tumor invasion of adjacent structures.⁵
• PET-CT scan — Positron emission tomography combined with CT identifies areas of increased metabolic activity, helping determine disease extent and detect distant metastases. PET-CT is essential for staging.⁵
• MRI — Magnetic resonance imaging provides superior soft-tissue contrast and is used to evaluate diaphragmatic invasion and chest wall involvement, particularly when surgical resection is being considered.⁵

Step 2: Tissue biopsy

A definitive mesothelioma diagnosis requires a tissue biopsy. Fluid cytology alone (analysis of pleural or peritoneal fluid) is insufficient for a reliable diagnosis in most cases. Biopsy methods include:

• Thoracoscopy (VATS) — Video-assisted thoracoscopic surgery allows direct visualization of the pleural space and collection of tissue samples. This is the preferred biopsy method for suspected pleural mesothelioma.⁵
• Laparoscopy — For suspected peritoneal mesothelioma, laparoscopic biopsy provides direct access to abdominal tumors.
• CT-guided core needle biopsy — A less invasive alternative when thoracoscopy is not feasible, though the smaller tissue sample may limit diagnostic accuracy.

Step 3: Pathological confirmation

Biopsy tissue undergoes immunohistochemistry (IHC) testing to distinguish mesothelioma from other cancers (particularly adenocarcinoma, which can mimic mesothelioma microscopically). Key IHC markers include calretinin, WT1, cytokeratin 5/6, and D2-40 (positive in mesothelioma) versus CEA, MOC-31, BerEP4, and TTF-1 (positive in adenocarcinoma).⁴

Pathology also determines the cell type — epithelioid, sarcomatoid, or biphasic — which is critical for treatment planning and prognosis estimation.

Mesothelioma staging uses the TNM (Tumor, Node, Metastasis) system established by the American Joint Committee on Cancer (AJCC) and the International Association for the Study of Lung Cancer (IASLC). A formal TNM staging system exists only for pleural mesothelioma; peritoneal mesothelioma uses the Peritoneal Cancer Index (PCI) for surgical planning.⁸

Most patients (approximately 60–70%) are diagnosed at stage III or IV because early-stage mesothelioma produces few or no symptoms. Early detection through routine screening of asbestos-exposed populations is an active area of research, with blood biomarkers such as mesothelin and fibulin-3 under investigation.⁵

Mesothelioma treatment typically involves a multimodal approach — combining two or more treatment types to maximize effectiveness. Treatment selection depends on the cancer's stage, cell type, anatomical location, and the patient's overall health and preferences.¹

Surgery

Surgical options for pleural mesothelioma include:

• Extrapleural pneumonectomy (EPP) — Removal of the affected lung, pleura, pericardium, and diaphragm. This radical procedure aims for complete macroscopic tumor removal but carries significant morbidity and mortality risk.¹
• Pleurectomy/decortication (P/D) — Removal of the pleural lining and visible tumor while preserving the lung. P/D is increasingly preferred over EPP due to lower perioperative mortality and comparable long-term outcomes.⁸
• Palliative procedures — Pleurodesis (fusing the pleural layers to prevent fluid accumulation) and indwelling pleural catheters provide symptom relief for patients who are not candidates for curative-intent surgery.

For peritoneal mesothelioma, cytoreductive surgery (CRS) with HIPEC is the standard of care at specialized centers, with 5-year survival rates exceeding 50% when complete cytoreduction is achieved.³

Chemotherapy

The standard first-line chemotherapy regimen for mesothelioma is pemetrexed combined with cisplatin (or carboplatin for patients who cannot tolerate cisplatin). This combination, established by the landmark 2003 trial, produces a median survival of 12.1 months compared to 9.3 months with cisplatin alone.⁹

Immunotherapy

Immunotherapy with nivolumab plus ipilimumab (Opdivo + Yervoy) received FDA approval in October 2020 for unresectable pleural mesothelioma based on the CheckMate 743 trial, which demonstrated a median overall survival of 18.1 months versus 14.1 months for chemotherapy.¹⁰

Radiation therapy

Radiation is used in mesothelioma treatment as adjuvant therapy after surgery (to reduce local recurrence), palliatively (to relieve chest wall pain or control tumor growth at specific sites), and prophylactically (to prevent tumor seeding along biopsy or surgical tracts).¹

Clinical trials

Ongoing clinical trials are investigating tumor treating fields (TTFields), targeted therapies, gene therapy, photodynamic therapy, and novel immunotherapy combinations. Patients should discuss clinical trial eligibility with their oncologist, as trials provide access to emerging treatments that may improve outcomes beyond current standard-of-care options.¹

Mesothelioma carries a guarded prognosis, with an overall 5-year survival rate of approximately 10–12%.¹ However, survival varies significantly based on several factors:

• Stage at diagnosis — Stage I patients treated with multimodal therapy have median survival times exceeding 21 months, while stage IV patients have a median survival of 6–12 months.⁸
• Cell type — Epithelioid mesothelioma has the best prognosis (median survival 14–19 months), followed by biphasic (10–13 months) and sarcomatoid (6–8 months).⁴
• Anatomical type — Peritoneal mesothelioma treated with CRS/HIPEC has the best outcomes, with 5-year survival rates of 50–65% at high-volume centers. Pericardial mesothelioma has the poorest prognosis, with median survival under 6 months.³
• Treatment approach — Patients who receive multimodal therapy (surgery + chemotherapy + radiation) have significantly better outcomes than those who receive single-modality treatment or best supportive care alone.⁸
• Patient factors — Younger age, good performance status (ECOG 0–1), female sex, and absence of chest pain at presentation are associated with better survival.⁴

Prognosis has improved modestly over the past two decades. The introduction of pemetrexed/cisplatin chemotherapy in 2004, the growing adoption of lung-sparing P/D surgery, the FDA approval of nivolumab/ipilimumab immunotherapy in 2020, and the development of HIPEC for peritoneal disease have each contributed to incremental survival gains.¹⁰

Because asbestos exposure is the primary cause of mesothelioma, prevention centers on avoiding asbestos exposure and adhering to regulatory protections:⁶

• Workplace regulations — OSHA sets permissible exposure limits (PEL) for asbestos at 0.1 fibers per cubic centimeter over an 8-hour time-weighted average. Employers must provide respiratory protection, exposure monitoring, and asbestos awareness training to workers who may encounter asbestos-containing materials.⁷
• Asbestos abatement — Buildings constructed before 1980 may contain asbestos in insulation, floor tiles, roofing materials, pipe wrap, and other components. Professional asbestos abatement should be performed by licensed contractors before renovation or demolition. Homeowners should never disturb suspected asbestos materials themselves.⁷
• EPA regulations — The EPA regulates asbestos under the Clean Air Act (National Emission Standards for Hazardous Air Pollutants), the Toxic Substances Control Act, and the Asbestos Hazard Emergency Response Act (AHERA), which requires inspection and management of asbestos in schools.⁷
• Military and veterans — Veterans, particularly those who served in the Navy, are at elevated risk due to widespread asbestos use in ships, shipyards, and military facilities. Veterans should inform their VA healthcare providers of any potential asbestos exposure during service.⁷
• Secondary exposure prevention — Workers in asbestos-related occupations should shower and change clothes at the worksite to avoid carrying fibers home to family members. Contaminated clothing should never be laundered at home.⁶

For individuals with known asbestos exposure, there is currently no proven screening method for early detection of mesothelioma. Research into blood biomarkers (soluble mesothelin-related peptides, fibulin-3, high-mobility group box protein 1) continues, but none have achieved sufficient sensitivity and specificity for routine clinical use.⁵

A mesothelioma diagnosis is life-altering for patients and their families. The following resources and strategies can help manage the physical, emotional, and practical challenges of living with this disease:

• Seek specialized care — Treatment outcomes are significantly better at high-volume mesothelioma centers with experienced thoracic oncologists, surgeons, and multidisciplinary teams. Consider a second opinion at a National Cancer Institute-designated cancer center.
• Palliative care — Palliative care is appropriate at any stage of mesothelioma, not just end-of-life. It focuses on managing pain, breathing difficulties, nutritional issues, and emotional distress. Early palliative care referral has been shown to improve both quality of life and survival in thoracic cancers.¹
• Nutritional support — Maintaining adequate nutrition is challenging during treatment. A registered dietitian experienced in oncology can help manage treatment-related appetite loss, nausea, and weight changes.
• Pulmonary rehabilitation — For pleural mesothelioma patients, pulmonary rehabilitation (breathing exercises, oxygen therapy, physical conditioning) helps maintain respiratory function and physical endurance.
• Emotional and psychological support — Depression and anxiety are common in mesothelioma patients. Support groups, individual counseling, and organizations such as the Mesothelioma Applied Research Foundation provide peer support and educational resources.
• Legal and financial resources — Patients diagnosed with mesothelioma due to asbestos exposure may be entitled to compensation through asbestos trust funds, personal injury lawsuits, or VA disability benefits. There are deadlines (statutes of limitations) for filing legal claims, so early consultation with an experienced mesothelioma attorney is advisable.
• Advance care planning — Discussing treatment goals, advance directives, and end-of-life preferences with the medical team and family members early in the treatment process ensures that the patient's wishes are respected throughout the course of care.

Patients and families can find additional information and support through the patients and families resource page.