Mesothelioma Stages

After making a mesothelioma diagnosis, doctors need to know the extent of the patient’s cancer, specifically how much cancer there is and where it is located in the body. This process is known as staging. There are four mesothelioma stages, ranging from stage 1 (early stage) to stage 4 (late stage). Knowing the stage of mesothelioma helps doctors develop the most effective treatment plan as well as overall prognosis or chance of being cured.

What Are Mesothelioma Stages?

Once a patient has been diagnosed with malignant mesothelioma, doctors will attempt to determine how far their cancer has spread and how best to treat it through a process called cancer staging.

The stages of mesothelioma, ranging from stage 1 to stage 4, describes the extent of cancer spread in the body. Stage 1 is the earliest malignant mesothelioma stage with the least cancer spread, while stage 4 is the most advanced.

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Video Summary: Registered Nurse Amy Fair discusses the 4 stages of mesothelioma and why it's important to talk to your doctor about mesothelioma staging. View Transcript.

What are the stages of mesothelioma?

There are 4 stages of mesothelioma just as there are in most cancers. Stage 1 the mesothelioma is contained within the pleura. Stage 2 the disease has come outside the pleura and invaded into the fatty tissue of lung or the diaphragm. Stage 3 is where it’s metastasized into local organs and stage 4 is where it’s metastasized into distant organs, limp nodes and tissue.

Staging is important in mesothelioma as is in any cancer. It drives your prognosis; it drives your treatment modalities. It’s important to know if you’re a surgical candidate and the staging of your disease drives that decision. It’s important to discuss staging after you’ve had your CT or PET scan with your surgeon or oncologist.

Each patient’s mesothelioma may behave in unique ways, but according to the American Cancer Society (ACS), similarly-staged mesothelioma tends to have a similar outlook and is often treated using the same methods.

Quick Facts About Mesothelioma Stages

  • Pleural mesothelioma is the only type of mesothelioma that has been officially staged.
  • Although it has no official staging, peritoneal mesothelioma is sometimes unofficially staged to help patients understand their disease outlook.
  • In the United States and many other countries, mesothelioma is staged using the Tumor Node Metastasis (TNM) System — a system used to stage nearly every type of solid tumor cancer.
  • Stage 4 pleural mesothelioma is the only cancer stage considered unresectable (unable to be surgically removed).

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Mesothelioma Staging Systems

A mesothelioma staging system is an established method for determining how far mesothelioma has spread in a patient’s body. Currently, the only officially-staged mesothelioma type is pleural mesothelioma. Other types of mesothelioma are extremely rare, and not enough is known about their progression to accurately stage them.

Each staging system has its own way of describing the progression of pleural mesothelioma.

The most commonly used mesothelioma staging systems are:

  • Tumor-node-metastasis (TNM) staging system
  • Butchart staging system
  • Surveillance, Epidemiology, and End Results (SEER) staging system

The Brigham staging system was created specifically for staging pleural mesothelioma, but it is not commonly used anymore.

TNM Staging System

According to the ACS, the most commonly used staging system for malignant pleural mesothelioma is the TNM system, regulated by the American Joint Committee on Cancer (AJCC) and the Union for International Cancer Control (UICC).

The TNM system measures cancer progression based on three key factors:

  • Size of the main tumor (T): How far the cancer has spread in the pleura (lining of the lung), whether it has spread to nearby areas in the chest, whether it can be removed with surgery, etc.
  • Spread to nearby lymph nodes (N): Whether the cancer has spread to nearby lymph nodes
  • Spread to distant sites (M): Whether the cancer has spread to distant areas of the body (metastasized) such as the bones, liver, or lung on the other side of the body

Numbers and/or letters after the T, N, and M detail the progression of these three factors. For example, T1 describes a tumor that has not spread widely.

Some mesothelioma stages also have sub-stages, with earlier letters representing an earlier stage of mesothelioma. For example, stage 3A mesothelioma is earlier than 3B.

Once a doctor determines a patient’s T, N, and M categories, they combine it to assign an overall stage (such as stage 2 mesothelioma).

Butchart Staging System

The Butchart system is the oldest mesothelioma staging system, designed in 1976 to stage pleural mesothelioma. It is based on a simple description of how far the disease has spread.

The Butchart system describes pleural mesothelioma stages in the following way:

  • Stage 1: Mesothelioma contained to the pleura
  • Stage 2: Mesothelioma spread to the chest wall or part of the chest between the lungs (mediastinum)
  • Stage 3: Mesothelioma spread to the peritoneum or diaphragm
  • Stage 4: Metastasized mesothelioma

While many countries have stopped using it in favor of the TNM system, the Butchart system is still used in some parts of the world.

SEER Staging System

In the past, mesothelioma was commonly staged using the SEER or Summary staging system.

According to the National Cancer Institute (NCI), this system is “the most basic way of categorizing how far a cancer has spread from its point of origin.”

It divides mesothelioma’s spread into local, regional, and distant metastasis (LRD) stages.

The SEER system describes pleural mesothelioma stages in the following way:

  • Local: Tumor confined to the pleura
  • Regional: Tumor has reached nearby tissue and/or lymph nodes
  • Distant: Mesothelioma cancer cells have spread to distant parts of the body

While it has largely been replaced by the TNM system, the SEER staging system is still very important for research on how mesothelioma progresses because decades of data were recorded using LRD stages.

Brigham Staging System

The Brigham staging system was designed specifically for staging pleural mesothelioma. It is focused on determining whether a patient’s tumors are surgically removable and whether the cancer has reached the lymph nodes.

The Brigham system describes pleural mesothelioma stages in the following way:

  • Stage 1: Resectable tumors with no spread to the lymph nodes
  • Stage 2: Resectable tumors with cancer cells that have reached the lymph nodes
  • Stage 3: Unresectable tumors that have spread to the chest wall, heart, diaphragm, or abdomen, with or without lymph node involvement
  • Stage 4: Mesothelioma that has metastasized (spread to distant parts of the body) with unresectable tumors

The Brigham system is not often used for mesothelioma diagnosis.

Pleural Mesothelioma Stages

According to the ACS, pleural mesothelioma patients make up roughly 80% of all mesothelioma cases. Pleural mesothelioma is staged based on the spread of the cancer.

Pleural mesothelioma spreads through:

  • Tissue: Cancer spreads from the mesothelium where it started to the tissue of nearby areas.
  • Lymph System: Spreads from the mesothelium into nearby lymph nodes located throughout the body such as in the armpits, neck, or groin. Once it gets into the lymph nodes, it can spread throughout the body via the lymph vessels.
  • Blood: Spreads from the mesothelium to the blood system, which allows it to travel throughout the body.

It is the only type of mesothelioma that has been well-researched enough to be officially staged using the TNM Staging System.

The TNM System generally describes the stages of pleural mesothelioma as such:

Stage 1

  • Remains on one side of the chest in the lining of the chest wall
  • Pleura may be cancer-free (1A)
  • May have spread to the pleura (1B)

Stage 2

  • In lining of the chest wall and the lymph nodes on one side of the body
  • May have also spread to the diaphragm and lungs
  • Has not reached distant parts of the body

Stage 3

  • Has spread past pleura into the deeper tissues
  • May have reached areas such as the abdominal lining or spine
  • May have spread to both sides of the body
  • Has spread to the lymph nodes
  • Has not reached distant parts of the body

Stage 4

  • May or may not have grown into nearby tissues
  • May or may not have spread to nearby lymph nodes
  • Has spread to distant organs

This staging helps mesothelioma patients understand what to expect as their disease progresses and helps doctors create the most effective treatment plan for their patients.

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Stage 1 Pleural Mesothelioma

Stage 1 mesothelioma is the earliest point in mesothelioma’s development. During this stage, the cancer has not spread very far.

Stage 1 mesothelioma has 2 sub-stages:

  • Stage 1A: Mesothelioma remains in the pleura on one side of the chest cavity and may or may not have begun growing into the tissues of the lung or diaphragm. It has not spread to nearby lymph nodes or distant parts of the body.
  • Stage 1B: Mesothelioma has grown into nearby tissues such as the lung and chest wall, but it remains on one side of the chest. The cancer still has not spread to nearby lymph nodes or distant parts of the body.

Stage 1 mesothelioma patients have the best prognosis and are usually good candidates for curative treatments such as surgery.

Stage 2 Pleural Mesothelioma

Stage 2 mesothelioma describes cancer that is still contained to one side of the body but has spread outside the pleura, into deeper tissues and nearby lymph nodes.

Stage 2 is still considered an early stage of mesothelioma when most curative surgeries can still be performed.

Stage 3 Pleural Mesothelioma

During stage 3 mesothelioma, cancer has either spread deeper into surrounding tissues, spread to more lymph nodes, or both.

Stage 3 mesothelioma has 2 sub-stages:

  • 3A: Mesothelioma has grown into nearby tissues and has invaded some tissues on the other side of the chest. It has only spread to lymph nodes on the side of the body where the main tumor originated. It has not spread to distant body parts.
  • 3B: Mesothelioma either has spread to lymph nodes on the other side of the body or it has grown so deep into surrounding tissues that it can no longer be surgically removed. Regardless, it has not spread to distant parts of the body.

At this stage of mesothelioma, some patients may still be able to undergo curative treatments. However, doctors will likely recommend treatments to potentially control the cancer and help manage symptoms (palliative care).

Stage 4 Pleural Mesothelioma

The most advanced stage of mesothelioma is stage 4 mesothelioma. It marks the point when cancer cells have metastasized, traveling through the lymph nodes or blood vessels and taking root in distant parts of the body.

Even if the main tumor remains fairly small and mesothelioma has not reached the lymph nodes, it is considered stage 4 if metastasis has occurred.

At this stage, curative surgeries are nearly always unavailable to mesothelioma patients since the cancer is nearly impossible to completely remove. However, palliative treatments to potentially control the cancer and relieve symptoms may still improve a patient’s quality of life.

Peritoneal Mesothelioma Stages

There is no officially recognized staging system for peritoneal mesothelioma. This mesothelioma type makes up less than 10% of all cases, according to a 2017 ACS report, so research on how it progresses is not as plentiful as it is for pleural mesothelioma.

Peritoneal mesothelioma also presents staging challenges because it advances in an unusual way, often remaining in the abdomen instead of spreading to other parts of the body.

In some cases, peritoneal mesothelioma is classified using the SEER system’s LRD model (local, regional, distant metastasis).

However, Professor Tristan D. Yan proposed a new “TNM” staging system for peritoneal mesothelioma in 2011. Even with this proposal, more data is needed before it becomes an official staging system.

The proposed TNM staging for peritoneal mesothelioma is based on three factors:

  • How much the mesothelioma is affecting the patient’s health
  • How much the cancer has spread within the abdomen
  • How much the cancer has spread beyond the abdomen

With the help of a diagnostic and prognostic tool called the peritoneal carcinomatosis index (PCI), doctors can translate these traits into four distinct stages.

This grouping helps doctors better determine the prognosis for a peritoneal mesothelioma patient.

Pericardial Mesothelioma Stages

Pericardial mesothelioma is a very rare form of mesothelioma. As a result, there is not enough knowledge about the disease to properly stage it.

The disease may, instead, be described as localized, regional, or distant using the SEER staging system. Doctors may also simply determine whether the cancer can be surgically removed and/or if it has spread to other parts of the body.

Most patients are diagnosed with pericardial mesothelioma after autopsy. Even when individuals receive a diagnosis while alive, their cancer is often detected at an advanced stage resulting in a poor prognosis.

Testicular Mesothelioma Stages

Testicular mesothelioma is extremely rare, so, like pericardial mesothelioma, it has no official staging system.

Doctors may look at whether or not a patient’s mesothelioma has metastasized to determine the individual’s outlook.

Diagnosing Mesothelioma Stage

Doctors use the results of a patient’s physical exam, biopsy, and imaging tests to confirm a mesothelioma diagnosis as well as to stage it.

Imaging tests — pictures of the inside of a patient’s body taken using X-rays, sound waves, and other methods — help doctors more clearly see the location and spread of a patient’s mesothelioma.

Imaging tests that may help diagnose the mesothelioma stage are discussed below.

Computed Tomography (CT) Scan

CT scans use X-rays to make detailed images of the inside of a patient’s body. Doctors often use these scans to help diagnose mesothelioma, find its exact location, and help determine if it has spread to other organs. This information often reveals if a patient’s mesothelioma is resectable.

Magnetic Resonance Imaging (MRI) Scan

MRI scans use radio waves and powerful magnets to take detailed images of the body’s tissues. These highly detailed images may help show the exact location and extent of a patient’s mesothelioma. According to the ACS, MRI scans may be especially helpful when determining if pleural mesothelioma has spread to the diaphragm.

Positron Emission Tomography (PET) Scan

PET scans work by using a special camera that picks up radioactivity in a patient’s body. Before the scan, patients are injected with a low-dose radioactive sugar that is absorbed more quickly by cancer cells. The picture from a PET scan can help a doctor see if mesothelioma has spread to lymph nodes or other areas.


Machines able to do a PET and CT scan at the same time allow doctors to compare places where cancer may be concentrated (PET scan) with a detailed image (CT scan).

By helping doctors determine a patient’s mesothelioma stage, these imaging tests also help doctors decide what treatments will be most effective for an individual.

Mesothelioma Treatments by Stage

When it comes to deciding options for mesothelioma treatment, the stage of a patient’s mesothelioma plays a major role. It may determine if the cancer is resectable and influence whether an individual is healthy enough to undergo major surgery or other invasive cancer treatments.

Depending on the extent of the mesothelioma, the patient’s personal wishes, and other factors, doctors may focus mesothelioma treatment on curative or palliative options.

Stage 1 Mesothelioma Treatment

According to the ACS, doctors do not always immediately begin treatment on individuals with very early-stage cancer.

Doctors may recommend closely watching mesothelioma instead of treating it if it is:

  • At an early stage
  • Not causing symptoms
  • Developing slowly

If the cancer begins growing more quickly or starts to cause symptoms, doctors will begin treatment.

Stage 1 mesothelioma may be treated with:

  • Surgery
  • Chemotherapy
  • Radiation

In most cases, stage 1 pleural mesothelioma is potentially resectable. However, many factors may influence a patient’s eligibility for mesothelioma surgery, including their cancer cell type, the location of the tumors, and the patient’s overall health.

Stage 2 Mesothelioma Treatment

Many stage 2 mesothelioma patients are also good candidates for curative surgery, as the cancer has not spread far into the tissues.

As with stage 1, treatment for stage 2 mesothelioma includes:

  • Surgery
  • Chemotherapy
  • Radiation

Surgery may be especially beneficial for early-stage mesothelioma patients. According to the ACS, “surgery is more likely to have long-term benefits in early-stage cancers, where there’s a better chance that most or all of the cancer can be removed.”

Stage 3 Mesothelioma Treatment

Stage 3 mesothelioma may be more difficult to treat, especially stage 3B. Many cases of stage 3 mesothelioma are no longer resectable, lowering a patient’s life expectancy.

However, some stage 3 patients are still good candidates for curative surgery.

While the ACS reports that mesothelioma doctors do not agree on the effectiveness of chemotherapy or radiation therapy for mesothelioma, they are often used as the main treatments for patients who cannot undergo surgery and may extend life or relieve symptoms.

Stage 4 Mesothelioma Treatment

Stage 4 mesothelioma cannot be removed completely with surgery because the cancer is no longer contained to one area.

Mesothelioma chemotherapy is usually the main treatment for stage 4 mesothelioma patients, relieving symptoms and potentially shrinking or slowing the cancer’s growth.

According to the ACS, “surgery may also be helpful for some later-stage cancers, but the benefits are more likely to last only a short time.”

Because curative treatment for stage 4 mesothelioma is often limited, patients may benefit from newer treatments or experimental treatments through clinical trials.

Other stage 4 mesothelioma treatments may include:

  • Tumor Treating Fields (TTF)
  • Immunotherapy
  • Targeted therapy

Although these treatments may help people live longer, they are highly unlikely to cure mesothelioma.

Patients may also seek palliative treatment — treatment conducted in order to reduce the pain and discomfort caused by mesothelioma, rather than extend life.

Palliative stage 4 mesothelioma treatments may include:

  • Medication: May help relieve pain
  • Pleurodesis: May reduce fluid buildup
  • Radiation: May help shrink tumors, relieving pain
  • Thoracentesis/paracentesis: May reduce fluid buildup

As their mesothelioma progresses, patients should let their doctor know if they are experiencing any pain or discomfort so that they can remain as comfortable as possible.

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Mesothelioma Treatment Can Help at Any Stage

Mesothelioma stage is an important factor in determining a patient’s cancer outlook and treatment plan.

Most patients are diagnosed at a later mesothelioma stage, but as emerging treatment options like targeted therapy continue to improve and become available to more people, patients at all stages of mesothelioma may look forward to longer, healthier lives.

Mesothelioma Support Team
Reviewed by:Dr. Assuntina Sacco

Board-Certified Oncologist

  • Fact-Checked
  • Editor

Assuntina Sacco, MD is an Associate Professor of Internal Medicine at the University of California, San Diego (UCSD) Moores Cancer Center, where she also serves as the Medical Director of Infusion Services. She is a board-certified medical oncologist trained to treat all solid tumor types, with the use of chemotherapy, immunotherapy, targeted therapy, and clinical trials.

Dr. Assuntina Sacco is an independently paid medical reviewer.

Mesothelioma Hope was founded by a team of advocates to educate people about this aggressive form of cancer. Mesothelioma affects thousands of people each year. We help give hope to those impacted by mesothelioma.

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