What Are the Stages of Mesothelioma?

The stages of mesothelioma describe the size of tumors and how far they have spread. They are identified as stages 1, 2, 3 and 4. The location and size of tumors directly impact a patient’s symptoms. Pleural mesothelioma is the only type with an official 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 ask if their symptoms determine stage. Unfortunately, the symptoms of mesothelioma are not correlated with individual cancer stages.

Mesothelioma diagnoses often don’t occur until the later stages of the disease. That is because early stages typically don’t cause symptoms. The cancer is small in the early stages. It does not affect the body as do the larger, late-stage tumors.

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. They also show if treatments, such as surgery, will benefit a mesothelioma patient.

Stage 1 Pleural Mesothelioma

Stage 1 mesothelioma tumor progression

In early-stage malignant pleural mesothelioma, the cancer has not spread past the outer lung lining. Major surgery to remove the tumor is usually the first line of treatment. Stage 1 mesothelioma prognosis and life expectancy are 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. Stage 1B tumors extend further into the lungs, chest wall, the mediastinum between the lungs or the diaphragm muscle under the lungs. 

Identifying cancer is tough at this early stage. Tumors are too small to cause pain or breathing difficulties. Patients with a known history of asbestos exposure undergo screening before experiencing symptoms. Stage 1 mesothelioma 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.

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

The prognosis in stage 2 mesothelioma is generally favorable. 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. This improves 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. But 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 substage: 3A and 3B. Stage 3A tumors have grown and spread deeper to nearby tissues, organs and lymph nodes. But some patients may still qualify for surgery.

Stage 3B tumors have more extensive lymph node involvement. This lessens the surgical benefits. The median life expectancy at stage 3 is 17.9 months with surgery.

Symptoms worsen in stage 3 mesothelioma. These symptoms 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. Most stage 3 patients are ineligible for surgery. Palliative options may control pain, improve quality of life and extend survival. Stage 3 patients can join clinical trials to receive experimental chemotherapy drugs.

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.

Curative treatments are limited. Aggressive surgery for tumor removal is not beneficial at this stage. Palliative care options, including chemotherapy, surgery or radiation therapies. These can reduce symptoms and improve quality of life. Clinical trials could offer experimental treatments.

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.

The median life expectancy for stage 4 mesothelioma is 14.9 months.

Metastasis in the Final Stage of Mesothelioma

Metastasis means cancer has spread to a different body part from where it first developed. Once metastasis has occurred, doctors classify cancer as stage 4. This is 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. It may spread to the chest cavity or the abdominal cavity. The cancer rarely spreads to distant body parts such as the brain.

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Pleural Mesothelioma Staging Systems

Mesothelioma specialists use CT, MRI imaging and surgical biopsy to identify cancer stage. The tests also help determine the best treatment. Doctors base treatment plans on tumor location, size and lymph node involvement. 

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

TNM Staging System

The TNM staging system is the is the gold standard for staging malignant pleural mesothelioma. Doctors will also show 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. The goal was to identify which pleural patients would respond best to 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 to help doctors identify which pleural patients could handle aggressive treatment options. He understood 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 uses a unique system to classify mesothelioma. It determines stage by the extent of the disease furthest from its starting point. 

SEER stages include local, regional and distant. These are 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.

Peritoneal, Pericardial & Testicular Mesothelioma Staging

Peritoneal mesothelioma does not have an official staging system. But doctors use the TNM system. Pericardial and testicular mesothelioma have no staging systems because of their rarity. 

Peritoneal Mesothelioma Staging

Researchers are working on a TNM staging system for peritoneal mesothelioma. The system will define tumor, lymph node and metastasis development within the abdomen. Many doctors use the TNM system to stage peritoneal patients. Other may use a more straightforward approach that defines only an early and late stage.

Other doctors use the Peritoneal Cancer Index. The PCI determines a score based on tumor size in 13 different regions throughout the abdomen.

A 2020 study published in Scientific Reports shows PCI is an accurate tool for predicting prognosis and a patient’s response to treatment.

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.

Lack of data in the early stages is makes it tough to create a staging system for pericardial mesothelioma. 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. 

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 mesothelioma treatment plans. They also evaluate your age and overall health. Doctors will continue to restage your cancer as treatment or disease progresses.

Doctors also use staging to help inform a patient’s prognosis. Early-stage mesothelioma has a better prognosis. It also means prolonged survival. The extent of disease determines the likelihood of success with the available treatments.

“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


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

Resectable staging is when surgery is a treatment option. That means doctors can perform major surgery to remove cancer during the first line of treatment. If staging results show that surgery is no longer an option, doctors refer to the outcome as nonresectable staging.

Late-stage mesothelioma tumors at stages 3 and 4 have grown and spread. Surgical removal becomes impossible without taking out vital organs. In other words, surgery could be life-threatening for people with late-stage mesothelioma.

Chemotherapy and Immunotherapy

Chemotherapy and immunotherapy are available to patients at any stage of mesothelioma. Both are more effective at reducing tumors and stopping 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. They also prevent symptoms from worsening.

Radiation Therapy

Radiation therapy is available at any stage of mesothelioma. But 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.

The goal of radiation in late-stage mesothelioma is to shrink painful tumors growing into the chest wall. Palliative treatments such as radiation therapy provide significant pain relief.

Clinical Trials

Clinical trials test a variety of treatments for all stages of mesothelioma. Trials also seek patients who tried previous treatments or had no prior therapy.

These experimental trials offer patients access to new, innovative therapies for mesothelioma. Ask your doctor if you qualify for a clinical trial.

Common Questions About the Stages of Mesothelioma

Is stage 4 mesothelioma always terminal?

Mesothelioma is a terminal cancer because it has no cure. Treatment can be painful and varies between patients, but remission is possible. Palliative treatment options may 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 accepted method for pleural mesothelioma staging. TNM stands for Tumor Nodule Metastasis. It measures extent of tumor growth into organ tissues, lymph nodes and distant sites in the body.