What Are the Stages of Mesothelioma?

The stages of mesothelioma describe the size of tumors and how far they have spread. The location and size of tumors directly impact a patient’s symptoms.

Pleural mesothelioma is the only type that has an officially adopted cancer staging system.

The stages of pleural mesothelioma are:

  • Stage 1: Early tumor growth occurs along the mesothelial lining of one lung.
  • Stage 2: Cancer has spread to nearby lymph nodes.
  • Stage 3: Tumors have invaded deeper tissues in nearby organs and distant lymph nodes.
  • Stage 4: Metastasis is present, and tumors have formed at distant sites in the body.

People often wonder if they can determine their stage based on their symptoms. Unfortunately, the symptoms of mesothelioma are not strongly correlated with individual cancer stages.

Mesothelioma diagnoses often don’t occur until the later stages of the disease because the early stages typically cause no symptoms. The cancer is small in the early stages and does not affect the body as larger, late-stage tumors do.

Cancer staging is a crucial part of malignant mesothelioma diagnosis and treatment. Pathologists use biopsy samples to complete tumor grading and differentiation. Oncologists use these results with imaging scans to determine the cancer stage and whether a patient will benefit from mesothelioma treatments such as surgery.

Stage 1 Pleural Mesothelioma

Stage 1 mesothelioma tumor progression

Early-stage malignant pleural mesothelioma means cancer has not spread beyond the outer lung lining, and major surgery to remove the tumor is usually the first line of treatment. Stage 1 mesothelioma prognosis and life expectancy are significantly better than in later stages. The median life expectancy at stage 1 is 22.2 months with surgery.

Stage 1 mesothelioma includes two substages: 1A and 1B. Stage 1A tumors develop on one side of the chest within the pleural layers. The more advanced stage 1B tumors extend further into the lungs, chest wall, the mediastinum between the lungs or the diaphragm muscle under the lungs. 

It is challenging to catch cancer this early because tumors are too small to cause pain or breathing difficulties at this stage. Patients with a known history of asbestos exposure undergo screening before experiencing symptoms. After diagnosis, stage 1 mesothelioma multimodal treatment includes a combination of surgery, chemotherapy or radiation therapy.

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Stage 2 Pleural Mesothelioma

Stage 2 mesothelioma tumor progression
Stage 2 mesothelioma spreads locally and develops in nearby lymph nodes.

The prognosis in stage 2 mesothelioma is generally favorable, and most treatment options are still available. Symptoms in stage 2 are uncommon, but if present, may be more noticeable than in stage 1. Stage 2 tumors have spread beyond the mesothelial lining and into nearby lymph nodes. Tumors remain small enough for surgical removal, which positively impacts life expectancy for mesothelioma patients.

It is generally rare for symptoms to appear in stage 2, and most symptoms usually arise in stage 3. Stage 2 pleural mesothelioma symptoms, such as difficulty breathing during exercise or mild cough, may resemble the common cold. Peritoneal patients may lose weight or feel bloated. Doctors treat stage 2 mesothelioma with surgery, chemotherapy and radiation therapy. The same multimodal approach to treatment used at stage 1 is also an option in stage 2. The median life expectancy at stage 2 is 20 months with surgery. However, those who respond well to aggressive treatment may live three years or longer.

Stage 3 Pleural Mesothelioma

Stage 3 mesothelioma tumor progression

Stage 3 mesothelioma includes two substages: 3A and 3B. Stage 3A tumors have grown and spread deeper to nearby tissues, organs and lymph nodes. However, some patients may still qualify for surgery. Stage 3B tumors have more extensive lymph node involvement, making surgical benefits less likely. The median life expectancy at stage 3 is 17.9 months with surgery.

Symptoms worsen in stage 3 mesothelioma and include difficulty breathing, dry cough, wheezing and chest pain. Peritoneal mesothelioma patients develop constipation or diarrhea, abdominal pain and bloating. Weight loss, fever and night sweats are common to both mesothelioma types.

Doctors typically treat stage 3 mesothelioma with chemotherapy because most stage 3 patients are ineligible for surgery. At this stage, doctors offer palliative options to control pain, improve quality of life and extend survival. Stage 3 patients can also join clinical trials for a chance to receive experimental chemotherapy drugs and immunotherapies.

Stage 4 Pleural Mesothelioma

Stage 4 mesothelioma tumor progression

By stage 4, cancer has spread beyond its origin to distant body parts such as the liver, brain, bones or elsewhere. Treatments are limited to palliative care options, including chemotherapy, surgery or radiation therapies that can reduce symptoms and improve quality of life.

Pleural symptoms in stage 4 mesothelioma include difficulty breathing, trouble swallowing and severe chest pain. Abdominal issues, such as digestive problems, abdominal swelling and bowel obstruction, are more common in peritoneal patients. Patients may also experience loss of appetite, weight loss, muscle weakness, nerve pain, night sweats, fever and fatigue.

Treatments and clinical trial options such as immunotherapy and chemotherapy for mesothelioma patients help people live up to one year or longer. Aggressive surgery for tumor removal is not beneficial at this stage. The median life expectancy for stage 4 mesothelioma is 14.9 months.

Metastasis in the Final Stage of Mesothelioma

Metastasis means that cancer has spread to a different body part from where it first developed, either locally or distantly. Once metastasis has occurred, doctors automatically classify cancer as stage 4, the last stage of mesothelioma. The most common sites of distant mesothelioma metastasis include the liver, kidneys and spleen. Unlike other cancers, mesothelioma tends to metastasize locally rather than distantly. Mesothelioma is more likely to spread throughout the body cavity where it originated, for example, the chest cavity or the abdominal cavity, rather than travel to distant body parts such as the brain.

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Pleural Mesothelioma Staging Systems

Mesothelioma specialists use multiple tests, such as CT and MRI imaging and surgical biopsy, to match patients to a cancer stage. These tests inform doctors on which treatment will be most beneficial based on tumor location, size and lymph node involvement. 

Various staging systems serve different purposes for measuring and classifying disease, but comparable stages between systems typically result in similar treatment options for the patient. 

TNM Staging System

The TNM staging system is the most widely used and accepted system for staging malignant pleural mesothelioma. The American Joint Committee on Cancer developed this system over eight iterations, replacing the other staging systems. The AJCC stage is the same as the TNM stage.

Doctors will also indicate staging in this system as clinical or pathological. The results from imaging tests and physical examinations determine the clinical stage. Surgeons define the pathological stage based on biopsy results found after surgery.

Brigham Staging System

Dr. David Sugarbaker developed the Brigham system at Brigham and Women’s Hospital in Boston. His objective was to help identify which pleural patients would respond best to mesothelioma surgery. 

Mesothelioma surgeons continue to use this system in conjunction with other methods for greater accuracy when determining a patient’s surgical eligibility. 

Butchart Staging System

Dr. Eric Butchart developed the Butchart system in the late 1970s to help doctors identify which pleural patients could handle aggressive treatment options. Butchart understood that patients with early-stage disease tolerated aggressive surgery and chemotherapy better than patients with advanced cancer. 

The Butchart system is no longer in use, but it helped doctors develop more modern staging systems that specialists use today. 

SEER Staging System

The Surveillance, Epidemiology and End Results (SEER) database hosted by the National Cancer Institute uses a unique system to classify mesothelioma by the extent of the disease furthest from its starting point. 

SEER stages include local, regional and distant, based on whether cancer is localized in the pleura, affecting regional lymph nodes or creating new sites in other areas. This system is no longer in practice for physicians but is still relevant in research.

Watch: Thoracic surgeon Dr. Jacques Fontaine explains how mesothelioma is staged and why staging is important.

Peritoneal, Pericardial & Testicular Mesothelioma Staging

Malignant pleural mesothelioma is the only type of mesothelioma with an officially adopted staging system. Mesothelioma specialists use staging methods adopted for other cancers to approximate the relative stage of nonpleural variants. 

The peritoneal cancer index, or PCI, helps doctors approximate the peritoneal mesothelioma stage based on progression in similar abdominal cancers. 

Due to their extreme rarity, pericardial and testicular mesothelioma have no appropriate staging systems. 

Peritoneal Mesothelioma Staging

A TNM staging system is in the works for peritoneal mesothelioma, which will define tumor, lymph node and metastasis development within the abdomen. Many doctors approximate the TNM system to stage peritoneal patients, while some may still use a more straightforward approach that defines only an early and a late stage.

Other doctors use the peritoneal cancer index, which assigns a stage to many other abdominal cancers. The PCI determines a score based on tumor size in 13 different regions throughout the abdomen.

According to a 2020 study published in Scientific Reports, PCI is an accurate tool for predicting prognosis and a patient’s response to treatment. In this way, PCI helps doctors make clinical decisions and is a substitute for an official staging system.

Pericardial Mesothelioma Staging

There is no staging system for pericardial mesothelioma because of its extreme rarity. There have been less than 150 cases of this variant, and it hasn’t amounted to enough data to create a staging system.

One of the challenges of creating a staging system for pericardial mesothelioma is the lack of data in the early stages of the disease. Up to 45% of these cases involved tumors that had spread to regional lymph nodes, lungs and kidneys by the time of diagnosis. 

Testicular Mesothelioma Staging

There have been less than 100 cases of testicular mesothelioma, and no official staging system exists for the variant. 

Because surgery is the preferred approach, doctors stage testicular mesothelioma based on a patient’s eligibility for surgery. They may also choose to describe testicular mesothelioma based on the TNM system for general testicular cancer. 

How Staging Affects Mesothelioma Treatment and Prognosis

Staging is the most significant factor doctors consider when developing your treatment plan. They also evaluate your age and overall health, but cancer’s stage primarily determines which mesothelioma treatments are appropriate for you. Doctors will continue to restage your cancer as treatment or disease progresses.

Doctors also use staging to help inform a patient’s prognosis. The extent of the disease determines the likelihood of success with the treatments available to you. An earlier malignant mesothelioma stage typically relates to a better prognosis and more prolonged survival.

“The way we determine the stage is with a CT or PET scan. If we see the mesothelioma is only in the chest, the best treatment is usually a combination of surgery and chemotherapy.”
Dr. Jacques Fontaine
Watch: Dr. Jacques Fontaine explains how the stage of mesothelioma affects treatment options.


Early-stage mesothelioma tumors (stages 1 and 2) are small and haven’t spread far beyond their origin. Their smaller size makes them easier to remove with surgery and more manageable to target with chemotherapy and radiation therapy. Immunotherapy is also more effective when tumors are small.

Staging that allows for surgery as a treatment option is termed resectable staging and means doctors can perform major surgery to remove cancer during the first line of treatment. If staging results indicate that surgery is no longer an option, doctors refer to the outcome as nonresectable staging.

Late-stage mesothelioma tumors (stages 3 and 4) have grown and spread, so surgically removing them becomes impossible without removing vital organs. In other words, surgery could be life-threatening for people with late-stage mesothelioma.

Chemotherapy and Immunotherapy

These treatments are available to patients at any stage of mesothelioma. They are more effective at reducing tumor size and halting tumor spread at earlier stages, but they can still extend the survival rate for mesothelioma patients in the late stages.

Palliative chemotherapy and immunotherapy in later stages help reduce or maintain tumor size and prevent symptoms from worsening. 

Radiation Therapy

While radiation therapy is available at any stage of mesothelioma, the application and outcomes differ between the early and late stages. Doctors use radiation therapy for early-stage mesothelioma to prevent local recurrence after surgery.

Radiation aims to shrink painful tumors growing into the chest wall when used in late-stage pleural mesothelioma. Palliative treatments such as radiation therapy provide significant pain relief.

Clinical Trials

Clinical trials test a variety of treatments for all stages of mesothelioma. For example, some research studies require early-stage patients, while others look for late-stage patients. Trials are also available for patients who have tried previous treatments or have had no prior therapy. 

Clinical research trials offer access to new, innovative therapies for mesothelioma, including immunotherapy. Ask your doctor whether you may qualify for experimental treatment based on your stage and diagnosis.

Common Questions About the Stages of Mesothelioma

Is stage 4 mesothelioma always terminal?

Mesothelioma is considered a terminal cancer because it has no cure. Stage 4 mesothelioma, also known as end-stage cancer or late-stage cancer, is the most advanced form of the disease. Treatment can be painful and varies between patients, but remission is possible. Palliative treatment options, which can improve symptoms and quality of life, also are available.

How does staging impact a mesothelioma diagnosis?

Doctors use staging to develop mesothelioma treatment plans for a given diagnosis based on the extent of cancer progression. Physicians determine a patient’s mesothelioma prognosis by the stage of their cancer and their response to treatment.

Which staging system is used to stage for pleural mesothelioma?

The TNM staging system is the most commonly accepted method for pleural mesothelioma staging. The acronym TNM stands for Tumor Nodule Metastasis and measures the extent of tumor growth into organ tissues, lymph nodes and distant sites in the body.

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