Mesothelioma Stages

What Are the Stages of Mesothelioma Cancer?

Doctors classify malignant mesothelioma into four main stages. Stages of mesothelioma indicate how far cancerous tumors have progressed in the body. At the earliest stage, cancer is localized to one area. Later stages reflect how far the cancer has spread by the time of diagnosis.

Doctors can determine during mesothelioma diagnosis whether the cancer is stage 1, 2, 3 or 4. Stage 4 is the most advanced stage of malignant mesothelioma. Patients usually have stage 3 or 4 mesothelioma when diagnosed.

Does Mesothelioma Stage Change Over Time?

Staging does not change as the disease progresses. Doctors usually only assess the stage at diagnosis to help determine the best treatment plan.

You can think of cancer staging as the starting point in a trip. Once the trip is underway, even if road conditions shift, you do not go back and change the starting point. You adjust your route instead.

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How Is Pleural Mesothelioma Cancer Staged?

Doctors stage pleural mesothelioma with the TNM system, which scores the tumor's size and extent (T), lymph node involvement (N) and spread to distant sites (M), then combines the three into a stage from 1 to 4. The ninth edition of that system took effect on January 1, 2025. Pleural mesothelioma, which accounts for about 85% of cases, is the only type of mesothelioma with specific staging systems.

Most cancers are categorized into four stages. The four stages of pleural mesothelioma are:

• Stage 1: The tumor is localized to the mesothelial lining and has not spread.
• Stage 2: Cancer has spread to nearby organs, such as the lungs or diaphragm.
• Stage 3: Cancer cells have spread to nearby tissues, lymph nodes or organs.
• Stage 4: Cancer has spread to nearby and distant organs, tissues and lymph nodes.

Cancer staging occurs during the initial diagnosis. Mesothelioma doctors often stage the disease with set characteristics. The American Joint Committee on Cancer’s AJCC Cancer Staging Manual is the most commonly cited.

Pleural mesothelioma is the only type of mesothelioma with a unique mesothelioma staging system. Tumor, Nodes and Metastasis (TNM) is the primary mesothelioma staging system. Less frequently used systems include the Butchart and Brigham.

These staging systems generally indicate that earlier stages have better survival. But treatment options have expanded in recent years. Doctors can guide patients through all available therapies and how they may impact life expectancy and quality of life.

TNM Staging System

The TNM staging system is the most commonly used staging system for pleural mesothelioma. It is periodically reviewed and updated according to new mesothelioma research. To classify pleural mesothelioma stage, doctors look at:

• T: Tumor size and extent
• N: Lymph node involvement
• M: Metastasis to other parts of the body

• Stage 1: The cancer is only affecting one layer of the pleura, or lining of the lungs. Mesothelioma may have spread to the pericardium (lining of the heart), diaphragm or lung.
• Stage 2: Mesothelioma has spread to both layers of the pleura but is still localized to one side of the body. Tumors may have spread to nearby lymph nodes.
• Stage 3: Mesothelioma has spread to other tissues or organs, like the chest wall, esophagus or diaphragm. The cancer may have also spread to nearby lymph nodes on both sides of the body. Tumors have not spread to distant parts of the body at this stage.
• Stage 4: Mesothelioma has spread to more distant organs through the bloodstream. The cancer may impact the liver, bones or brain.

The TNM system also breaks down the four stages even further to include stages 1A, 1B, 3A and 3B. This update was intended to make it easier to estimate mesothelioma prognosis. The additional stages can also help doctors choose the most effective treatment options for each patient.

Updates to Pleural Mesothelioma Staging

In January 2025, the TNM staging system was updated to the 9th edition. These edits further refine the measurement of tumor growth and spread. For example, tumor growth along lung fissures may now mark a more advanced stage. If you were diagnosed before 2025, your doctor likely used the 8th edition. What do you need to know?

• The core framework remains the same
• Some revised criteria may affect staging for certain patients
• Most patients' staging will not be impacted

Your doctor can confirm which edition they used and if they should revisit your stage or treatment plan.

Other Pleural Mesothelioma Staging Systems

There are other systems for staging mesothelioma, although medical professionals rarely use them today. Once historically used for staging mesothelioma, these systems have largely fallen out of use:

• The Brigham system: Developed in 1993, focuses on surgical factors and disease spread
• The Butchart system: Introduced in 1976, stages pleural mesothelioma based on tumor location

What Are the Symptoms of Each Stage of Pleural Mesothelioma?

Many mesothelioma symptoms can be present at multiple stages. Some symptoms are more common in earlier stages. Other symptoms may develop in later stages.

Symptoms of Pleural Mesothelioma by Stage

Stage 1 and stage 2 symptoms include chest pain and difficulty breathing. Symptoms of stage 3 and stage 4 include chest pain, difficulty breathing, fatigue and weight loss. All stages may have general symptoms, including coughing up blood, difficulty swallowing, dry cough, fever, night sweats, pleural effusion and pleural plaques.

Did You Know? Life expectancy for stage 1 mesothelioma patients is significantly greater than for those in later stages. Surgery, chemotherapy and radiation can control stage 1 mesothelioma. Learn More About Mesothelioma Treatment

How Mesothelioma Stage Impacts Treatment and Prognosis

Stage is the strongest single predictor of how long someone with pleural mesothelioma is likely to live. According to the American Cancer Society's February 2026 analysis of National Cancer Institute (NCI) SEER data covering people diagnosed between 2015 and 2021, 5-year relative survival rates vary considerably depending on how far the cancer has spread at diagnosis.

Those categories are not the same as stages 1 through 4. SEER records how far a cancer has spread rather than its AJCC stage, so no U.S. registry publishes a 5-year survival rate for stage 1 or stage 2 specifically. A survival figure attached to a single numbered stage comes from one institution's patients, not from national data.

These numbers also describe people diagnosed at least five years ago, most of them before immunotherapy became a standard first-line option. Someone diagnosed today may do better than the figures suggest.

Mesothelioma stage plays a key role in treatment options and outlook. Early-stage diagnosis typically allows for more aggressive treatments, with later-stage treatments emphasizing palliative care. Medical advances continue improving the variety of late-stage treatment options.

• Early stage: Usually stages 1 and 2, when cancer is still localized. Patients often have diverse options, including certain surgeries and combination therapies.
• Later stage: Usually stages 3 and 4, when cancer has spread. Treatment generally involves chemotherapy, immunotherapy or both.

The link between early stage and aggressive surgery is weaker than it used to be. The MARS 2 trial, published in 2024, randomly assigned patients with resectable pleural mesothelioma to extended pleurectomy decortication plus chemotherapy or to chemotherapy alone, and found median survival of 19.3 months in the surgery group against 24.8 months in the chemotherapy-only group, with more serious complications after surgery. Surgery still has a role for carefully selected patients, but being diagnosed at an early stage does not by itself make an operation the right choice.

Doctors also look beyond the stage when building a mesothelioma treatment plan. Other factors like mesothelioma type and cell type are critical when choosing the right therapies.

No matter the stage, patients may also qualify for clinical trials. These studies explore newer, promising treatments like cancer vaccines and gene therapy. Talking with your care team can help you understand the full range of available options.

Stage 1 Mesothelioma Treatment

At this stage, treatment often focuses on removing as much cancer as possible and improving long-term outcomes. Depending on factors like the type of mesothelioma, stage 1 patients may undergo:

• Cytoreductive surgery (CRS)
• Extrapleural pneumonectomy (EPP), now rarely performed
• Heated intraperitoneal chemotherapy (HIPEC)
• Intravenous (IV) chemotherapy
• Pleurectomy/decortication (P/D)
• Radiation therapy

Stage 2 Mesothelioma Treatment

Stage 2 patients typically have several treatment options. Doctors often combine therapies for a more comprehensive approach. Depending on eligibility, stage 2 methods may include:

• Chemotherapy, including heated and IV methods
• Emerging therapies
• Immunotherapy
• Palliative care
• Radiation
• Surgery

Stage 3 Mesothelioma Treatment

Treatment at this stage usually aims to extend survival and manage symptoms. Doctors commonly recommend therapies that target the whole body. Stage 3 treatment plans may include:

• Chemotherapy, including heated and IV methods
• Immunotherapy
• Multimodal therapy
• Palliative care
• Paracentesis
• Pleurocentesis
• Surgery

Stage 4 Mesothelioma Treatment

At stage 4, care is focused on symptom relief, quality of life and extending survival. Treatment plans for stage 4 mesothelioma patients largely focus on systemic treatments. But some patients may still benefit from surgery-based approaches.

• Immunotherapy
• IV chemotherapy
• Palliative care
• Paracentesis
• Pleurocentesis
• Surgery

Late-stage and end-stage mesothelioma are not exactly the same. A diagnosis of stage 4 mesothelioma does not necessarily mean it is end-stage. Your doctor can explain how your diagnosis is classified and what you can do to prepare for next steps.

Ongoing Research for All Mesothelioma Stages

Mesothelioma researchers use clinical trials to investigate new treatment options for early- and late-stage patients. For example, the CheckMate 743 trial established nivolumab plus ipilimumab as a first-line option for unresectable pleural mesothelioma, and the IND.227/KEYNOTE-483 trial reported in 2024 that adding pembrolizumab to chemotherapy extended median survival from 16.1 to 17.3 months.

Ongoing clinical trials continue to test new treatments for all stages of mesothelioma.

Peritoneal Mesothelioma and Rare Asbestos Cancer Staging

Peritoneal, pericardial and testicular mesothelioma do not have their own unique staging systems. Doctors see fewer cases of these types of mesothelioma. As a result, they have done less research into staging these types.

Peritoneal Mesothelioma Staging

Doctors may stage peritoneal mesothelioma patients using the Peritoneal Cancer Index (PCI). This staging system classifies the cancer according to tumor size and number. Thirteen regions of the abdomen are analyzed and assigned a score. A higher combined score of these regions means a more extensive cancer.

Some mesothelioma doctors may use a modified version of the TNM system to stage peritoneal mesothelioma. This staging system is not yet widely accepted within the medical community. However, data suggest it may predict patient prognosis more accurately than PCI.

Pericardial and Testicular Mesothelioma Cancer Staging

Because they are rare, pericardial mesothelioma and testicular mesothelioma do not have their own staging systems. Researchers estimate 10 to 15 new pericardial mesothelioma diagnoses in the United States each year. Fewer than 300 cases of testicular mesothelioma have been described in medical literature.

Because these types of mesothelioma are so uncommon, researchers have not developed unique staging systems for them. Doctors may evaluate these with general cancer staging systems.

Staging Other Asbestos Cancers and Conditions

Doctors use the TNM system to stage asbestos lung cancer. Other asbestos cancers, such as laryngeal cancer and ovarian cancer, follow their own staging systems.

Asbestosis is a lung disease caused by asbestos exposure, not a type of cancer. Doctors generally do not use a staging system to assess asbestosis cases. But they may assign it a grade ranging from zero to four, with four being the most severe.

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