Types of Mesothelioma
Mesothelioma is named for the mesothelium — a thin layer of tissue that lines the internal organs and body cavities. Asbestos fibers that are inhaled or, less commonly, swallowed can become embedded in this tissue and, over decades, trigger malignant cell changes. The type of mesothelioma depends on which portion of the mesothelium is affected.
| Type | Location | % of Cases | Primary Symptoms |
|---|---|---|---|
| Pleural mesothelioma | Lining of the lungs (pleura) | ~75% | Chest pain, shortness of breath, persistent dry cough, pleural effusion (fluid around the lungs), fatigue |
| Peritoneal mesothelioma | Lining of the abdomen (peritoneum) | ~20% | Abdominal pain and swelling, nausea, unexplained weight loss, changes in bowel habits, ascites (abdominal fluid) |
| Pericardial mesothelioma | Lining surrounding the heart (pericardium) | <1% | Chest pain, heart palpitations, irregular heartbeat, shortness of breath, fatigue |
| Testicular mesothelioma | Tunica vaginalis (testicular lining) | <1% | Painless testicular mass, scrotal swelling |
Cell Types: Epithelioid, Sarcomatoid, and Biphasic
Regardless of location, mesothelioma tumors are further classified by the type of cells present. Epithelioid mesothelioma (approximately 70% of cases) grows more slowly and generally responds better to treatment. Sarcomatoid mesothelioma (10–15% of cases) is more aggressive and has a worse prognosis. Biphasic mesothelioma (15–20% of cases) contains both cell types; prognosis depends on which type predominates.
Symptoms to Watch For
Mesothelioma has an extraordinarily long latency period — the time between first asbestos exposure and the appearance of symptoms typically ranges from 20 to 50 years. This means that someone who worked with asbestos in the 1970s may not develop symptoms until the 2000s or 2010s. The long latency, combined with nonspecific early symptoms, frequently leads to delayed diagnosis.
Early-Stage Symptoms
Early symptoms are often mistaken for less serious conditions. Many patients initially attribute their discomfort to aging, a respiratory infection, or musculoskeletal pain. Common early symptoms include:
- Shortness of breath, particularly during physical activity
- Chest pain or tightness, often on one side
- Persistent dry cough or wheezing
- Mild fatigue or reduced exercise tolerance
- Low-grade fever
Advanced-Stage Symptoms
As the disease progresses, symptoms become more severe and distinctive:
- Significant pleural or abdominal fluid accumulation (effusion or ascites)
- Severe, worsening chest or abdominal pain
- Rapid and unintended weight loss
- Night sweats and high fever
- Difficulty swallowing (dysphagia) in pleural cases
- Hemoptysis (coughing up blood) in some cases
- Nerve pain or weakness in upper extremities (Pancoast syndrome)
If you have an asbestos exposure history and are experiencing any of these symptoms, inform your physician immediately and specifically mention your asbestos history. Many primary care physicians do not routinely ask about occupational asbestos exposure.
Diagnosis
Mesothelioma is notoriously difficult to diagnose because its symptoms mimic more common conditions and because pathologists must distinguish it from lung cancer, adenocarcinoma, and other malignancies. A definitive diagnosis requires tissue biopsy and specialized immunohistochemistry analysis.
Diagnostic Pathway
- Imaging: Chest X-ray may show pleural thickening or effusion. Low-dose CT scan provides more detail and is the preferred first imaging study. PET scan is used to assess disease spread in some cases.
- Fluid analysis: If pleural or abdominal effusion is present, fluid is withdrawn (thoracentesis or paracentesis) and analyzed for malignant cells. Cytology alone is often insufficient for a definitive mesothelioma diagnosis.
- Biopsy: A tissue biopsy is required for definitive diagnosis. This may be performed via video-assisted thoracoscopic surgery (VATS), CT-guided needle biopsy, or laparoscopy.
- Pathology and immunohistochemistry: The tissue sample is analyzed by a pathologist, ideally one with mesothelioma specialization. Immunohistochemical markers (calretinin, WT-1, D2-40) help confirm the diagnosis and distinguish mesothelioma from other cancers.
- Staging: Pleural mesothelioma is staged I through IV. Peritoneal disease uses the Peritoneal Cancer Index. Stage significantly affects treatment options and prognosis.
It is strongly advisable to seek a second opinion from a mesothelioma specialist or major cancer center. Mesothelioma is rare enough that many community hospitals and pathologists have limited experience with it; expert review can change diagnosis, staging, and treatment recommendations.
Treatment Options
While there is currently no cure for mesothelioma, treatment options have expanded and improved significantly over the past decade. Treatment decisions depend on cell type, stage, tumor location, and the patient’s overall health.
- Surgery: For eligible patients with early-stage pleural mesothelioma, extrapleural pneumonectomy (EPP) or pleurectomy/decortication (P/D) can remove the tumor mass. Peritoneal mesothelioma is treated with cytoreductive surgery combined with heated intraperitoneal chemotherapy (HIPEC), with some patients achieving long-term remission.
- Chemotherapy: The standard first-line regimen is cisplatin combined with pemetrexed (Alimta), which became the FDA-approved standard of care in 2003 and remains widely used.
- Immunotherapy: Nivolumab (Opdivo) plus ipilimumab (Yervoy) received FDA approval in 2020 for unresectable pleural mesothelioma, representing a significant advance for patients not eligible for surgery.
- Radiation: Used selectively as adjuvant therapy after surgery, for palliative symptom control, or as part of multimodal protocols.
- Clinical trials: Numerous trials are evaluating new immunotherapy combinations, CAR-T cell therapy, targeted agents, and delivery mechanisms. Patients should ask their oncologist about trial eligibility.
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Frequently Asked Questions
Asbestos exposure is the cause of virtually every case of mesothelioma. When asbestos fibers — particularly the needle-like amphibole fibers (amosite and crocidolite) — are inhaled or ingested, they can become permanently lodged in the lining of the lungs, abdomen, or heart. The body cannot break down these fibers, and over decades of chronic irritation and inflammation, the fibers trigger genetic mutations in mesothelial cells that eventually lead to malignant tumor growth. There is no known safe level of asbestos exposure; even short-term or low-level exposures have caused mesothelioma. Asbestos manufacturers knew of this risk for decades before regulatory action was taken and chose not to warn workers.
Definitive diagnosis requires a tissue biopsy analyzed by a pathologist with mesothelioma expertise. Imaging studies (CT scan, PET scan) are used to identify suspicious masses and fluid accumulation, but they cannot confirm mesothelioma — biopsy is essential. Because mesothelioma is rare and its symptoms mimic more common conditions, misdiagnosis is common. Patients suspected of having mesothelioma should strongly consider seeking evaluation at a major cancer center or NCI-designated cancer center where pathologists and oncologists have substantial mesothelioma experience. A second pathology opinion on biopsy material is advisable and often changes the diagnosis or staging.
There is currently no known cure for mesothelioma, but the disease is not uniformly fatal in the short term, and a small subset of patients achieve long-term survival or even apparent remission. The best outcomes are achieved in patients diagnosed at an early stage (Stage I or II) with epithelioid cell type, who are eligible for aggressive surgery combined with chemotherapy and/or immunotherapy. Peritoneal mesothelioma patients treated with cytoreductive surgery plus HIPEC have achieved 5-year survival rates above 50% in specialized centers — a remarkable improvement over outcomes from a decade ago. Immunotherapy approvals since 2020 have also extended survival for patients not eligible for surgery. Clinical trials are actively evaluating new treatment combinations. Early diagnosis and treatment at a specialized center offer the best chance of meaningful survival.