Mesothelioma Stages

Doctors stage mesothelioma according to factors that indicate its progression. The mesothelioma stages range from Stage 1 (most treatable) to Stage 4 (fewest options). The system for staging is different for each primary type of mesothelioma.


Written by Jenna Campagna, RN


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How Doctors Determine Your Stage

Diagnosing a stage involves tests to determine how advanced your mesothelioma is after discovering it. This is accomplished through conducting a CT scan, PET scan or other surgical diagnostic methods.

These tests allow doctors to see if the mesothelioma has spread beyond the point of origin. The spread of this cancer is known as mesothelioma metastasis and it’s important in staging.

The Basics of Mesothelioma Stages

The primary factor in how doctors stage mesothelioma is the level of metastasis. Mesothelioma forms primarily in one of two protective linings: the pleura (which separates the chest wall and lung cavity) or the peritoneum (which covers the abdominal cavity). The stages advance as the cancer moves further from these original sites.

If you have mesothelioma, knowing the stage is vital to determining your best treatment plan. The different stages provide boundaries for physicians as they recommend treatment options. You should always seek a second opinion, which may lead to a lower mesothelioma stage and more opportunities for treatment.

Pleural Mesothelioma Stages

Pleural mesothelioma stages are classified from stage 1 to stage 4. Stage 1 pleural mesothelioma is localized in the pleura. As the cancer spreads farther away from its point of origin, the pleural mesothelioma stages advance.

There are three staging systems used for pleural mesothelioma. The outline below will follow the Tumor, Node, Metastasis (TNM) Staging System.


Stage 1 Pleural Mesothelioma

Stage 1 pleural mesothelioma is categorized by the lack of metastasis and lymph node involvement. The tumors are also small in collective size. This stage is divided into 1A and 1B.

Stage 1A involves mesothelioma cells only on the pleura’s outer cell layer (parietal). Stage 1B involves diseased cells on the inner cell wall (visceral) as well. Curative treatment options are available for both 1A and 1B diagnoses.


Stage 1 Pleural Mesothelioma

The cancer is located on or in:

  • One side of the chest
  • The lining of the chest wall
  • The lining between the chest wall and lungs (pleura)
  • The lining of the diaphragm

Stage 2 Pleural Mesothelioma

Stage 2 pleural mesothelioma involves the cancer spreading beyond the pleura. The cancer is still localized to one side of the chest.

The tumors continue growing and replicating during this stage and often begin invading the lung cavity. The tumors also begin spreading toward the chest wall, which is known as diffuse chest wall invasion. Treatment options for this stage still include curative surgeries.


Stage 2 Pleural Mesothelioma

The cancer has spread to:

  • The surrounding lung tissue
  • Partial areas on the diaphragm
  • Lymph nodes (possibly)

Stage 3 Pleural Mesothelioma

Stage 3 pleural mesothelioma hasn’t spread to the other side of the chest, but there is definite metastasis to the lymph nodes. Stage 3 is more locally aggressive, meaning it has affected the nearby lung and may have also spread to other organs. Curative surgery is not always a treatment option for stage 3.

Similar to stage 1, this stage is split into 3A and 3B. The TNM system differentiates the two by how far the cancer has spread. While still considered localized metastasis, stage 3B often is more challenging to treat with surgery.


Stage 3 Pleural Mesothelioma

The cancer has likely spread to the surrounding tissue, such as:

  • Tissue between the ribs and lining of the chest wall
  • Fat in the area between the lungs
  • Soft tissue in the chest wall (not just the lining)
  • The sac surrounding the heart (pericardium)

Similar to Stage 1, this stage is split into 3A and 3B. The TNM system differentiates the two by how far the cancer has spread. While still considered localized metastasis, stage 3B often is more challenging to treat with surgery.


Stage 4 Pleural Mesothelioma

Stage 4 pleural mesothelioma is the most advanced stage of this cancer and involves distant metastasis. Patients may experience more serious symptoms, such as difficulty swallowing and coughing up blood.

Treatment options are limited due to how far the cancer has spread — and how difficult or harmful it is to remove tumors through surgery. The main treatment options for stage 4 patients are chemotherapy, radiation and pain-relief operations (such as draining fluid).


Stage 4 Pleural Mesothelioma

In this stage, the cancer has likely metastasized to the:

  • Lymphatic system
  • Opposite sides of the chest, diaphragm and peritoneum
  • Spine and distant organs
  • All organs within the chest cavity

Peritoneal Mesothelioma Stages

Peritoneal mesothelioma staging involves a different system than the one for pleural mesothelioma. Peritoneal mesothelioma rarely involves metastasis to lymph nodes, so doctors don’t rely on that characteristic for staging. They instead look at the extent of the tumors in the abdominal cavity and follow the peritoneal cancer index (PCI).

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What Is the Peritoneal Cancer Index?

The peritoneal cancer index is the primary staging system for peritoneal mesothelioma. It applies a score based on how far the cancer has spread within the abdomen.

13 Sections of the Abominal Cavity

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The PCI scores on a range of 0-39, with each of the 13 sections of the abdomen receiving a score between 0 and 3. If a section has no signs of mesothelioma, it receives a 0 score. If the section is overrun with tumors, then it receives a 3.

Some doctors simplify the PCI for patients’ understanding by correlating a score to one of the four pleural mesothelioma stages:

PCI OF 1-10


PCI OF 11-20


PCI OF 21-30


PCI OF 31-39


The lower the PCI score, the more treatment options are available. However, you should always receive a second opinion after your initial diagnosis.

Mesothelioma survivor Alexis K. was originally diagnosed with late-stage peritoneal mesothelioma. Her cancer was considered inoperable. A second opinion revealed a less-advanced stage. Alexis underwent curative surgery and as of 2020, she has survived for 12 years and counting.

Staging Systems

The three common systems used for staging pleural mesothelioma are the TNM, Butchart and Brigham. The primary staging system for peritoneal mesothelioma is the PCI.

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Mesothelioma TNM Staging

The TNM Staging System is used the most. It is a four-stage system developed by the American Joint Committee on Cancer (AJCC) and the International Union for Cancer Control (IUCC).

It evaluates three aspects of the cancer: the tumors’ size (T), lymph node involvement (N) and metastasis (M). Each aspect receives a classification to help doctors stage the disease.


The T category considers whether mesothelioma tumors grew within the pleural space and invaded nearby tissue:

  • TX means the tumors cannot be measured.
  • T0 means the tumors can’t be found.
  • T1, T2, T3 and T4 measure the tumors’ collective size and where the cancer has spread.


The N category focuses on lymph nodes:

  • NX means lymph node involvement can’t be evaluated.
  • N0 means there is no lymph node involvement.
  • N1, N2 and N3 are classifications when lymph node involvement occurs, with numbers ranging in how many are affected and how much they’ve swollen.


The M category focuses on metastasis to other areas of the body:

  • M0 means no metastasis has occurred (the disease remains local).
  • M1 means the mesothelioma has spread to distant organs or tissues.

The AJCC and IUCC update the TNM Staging protocol every six or eight years as cancer research and treatment evolves. The system was last updated in 2018 to include stage 1A and stage 1B.

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The Butchart System

Developed by Dr. Eric Butchart in 1976, the Butchart System is the oldest system for determining the stage of a mesothelioma case. It consists of four stages and focuses on the size of the tumors, rather than the number of cancer cells and tumors that have formed, or where they’ve spread.

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The Brigham System

Dr. David Sugarbaker, who passed away in 2018, developed the Brigham Staging System while working at Brigham and Women’s Hospital in Boston. This system focuses on whether surgery is an option for the patient. It is a four-stage system that looks at whether there is lymph node involvement.

The system considers location, size and spread of the cancer. Stage 1 and stage 2 patients are candidates for surgery. Stage 3 and stage 4 patients are not.

What Is the Next Step After Staging?

Once staging concludes, patients should review their treatment options with their primary doctor. Depending on the stage of your mesothelioma, you may be eligible for life-saving surgery.

If you are diagnosed in a stage that prevents you from receiving curative treatment, then you should consider getting a second opinion from a specialist. Second opinions for the stage of your cancer may provide new treatment options to extend life. Get connected to a specialist today using our free Doctor Match program.

Common Questions About the Stages of Mesothelioma

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What are the stages of mesothelioma?

There are four stages of mesothelioma. As the disease progresses and spreads further in the body, the stage increases:

  • Stage 1 involves tumors on one or both sides of the lungs’ lining, known as the pleura.
  • Stage 2 has tumors spreading into the lung cavity and possibly reaching lymph nodes.
  • Stage 3 involves tumors reaching distant lymph nodes, lung tissue and fat between the lungs.
  • Stage 4 has tumors on the opposite side of the chest, the diaphragm and the peritoneum.
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How are mesothelioma stages determined?

The stage of mesothelioma depends on how big the tumors are and how far they’ve spread in the body. Utilizing diagnostic imaging, doctors often focus on the size of the primary (original) tumor for staging this cancer. The stage of a diagnosis may affect the treatment options available to a patient.

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How is peritoneal mesothelioma staged?

For peritoneal mesothelioma, doctors use the peritoneal cancer index (PCI) to quantify the cancer’s scope within the abdominal cavity. Doctors score each of the 13 sections between 0 and 3 based on if the cancer has spread there. They add up the scores and correlate it to one of the four stages.

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What is the prognosis for each stage of mesothelioma?

The average survival rate decreases as the stage increases. For pleural mesothelioma:

  • Stage 1 average survival is 20 months.
  • Stage 2 average survival is 19 months.
  • Stage 3 average survival is 16 months.
  • Stage 4 average survival is 11 months.
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What are the end stages of mesothelioma?

The end stages of mesothelioma are the latter two stages, which are stage 3 and stage 4. Most people with mesothelioma are diagnosed in stage 3.

Last Edited: January 21, 2021.

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