Written By: Karen Ritter, RN BSN

Mesothelioma Stages

Doctors stage mesothelioma based on where it forms and how it progresses to other parts of the body. There are four mesothelioma stages: stage 1 and stage 2 are considered early stages; stage 3 and stage 4 are considered advanced stages. The staging system is different for the two primary types of mesothelioma.

Dr. Hassan Khalil

Medically Reviewed By

Dr. Hassan Khalil

Mesothelioma Thoracic Surgeon

Dr. Hassan Khalil

Medically Reviewed By

Dr. Hassan Khalil

Mesothelioma Thoracic Surgeon


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Important Facts About Mesothelioma Stages

  • There are four stages of mesothelioma, increasing as the cancer worsens.
  • The stage of mesothelioma depends on the size of tumors, how far they’ve spread and whether they’ve reached lymph nodes.
  • The stage determines which treatment options are best for a case.
  • Pleural mesothelioma and peritoneal mesothelioma are staged using two different staging systems.

How Doctors Determine the Four Stages of Mesothelioma Cancer

Staging mesothelioma begins with determining where the cancer has formed. Pleural mesothelioma forms in the lining of the lungs, and peritoneal mesothelioma forms in the lining of the abdomen. Once specialists have determined the location of the cancer, further testing will be conducted to learn how advanced your mesothelioma is. This is accomplished through a CT scan, PET scan or surgical methods.

These tests allow doctors to see how far the mesothelioma has spread and the size of tumors. The spread of this cancer is known as mesothelioma metastasis.

The Basics of Mesothelioma Cancer Stages

The primary factor in how doctors stage mesothelioma is where the cancer forms. Pleural mesothelioma is staged the same way as most other cancers, while the staging system used for peritoneal mesothelioma is specific to cancer of the peritoneum. 

Mesothelioma forms primarily in one of two protective linings: the pleura (between the chest wall and lung cavity) or the peritoneum (covers the abdominal cavity). Stages advance as the cancer moves further from these original sites.

Early-stage mesothelioma is considered stage 1 or stage 2, while advanced-stage mesothelioma are stages 3 and 4. Patients with early-stage mesothelioma may be eligible for more mesothelioma treatment methods than those diagnosed in later stages. 

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.

Staging Malignant Pleural Mesothelioma 

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

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

Stage 1 Mesothelioma

Stage 1 Pleural Mesothelioma

Stage 1 pleural mesothelioma has a 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 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.

Stage 1 Mesothelioma

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 Mesothelioma

Stage 2 Pleural Mesothelioma

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

The tumors often begin invading the lung cavity during this stage. They also spread toward the chest wall, which is known as diffuse chest wall invasion. Treatment options for this stage include curative surgeries.

Stage 2 Mesothelioma

Stage 2 Pleural Mesothelioma

The cancer has spread to:

  • The surrounding lung tissue
  • Partial areas on the diaphragm
  • Lymph nodes (possibly)
Stage 3 Mesothelioma

Stage 3 Pleural Mesothelioma

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

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 is more challenging for surgery.

Stage 3 Mesothelioma

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 between the lungs
  • Soft tissue in the chest wall (past 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 is more challenging for surgery.


Stage 4 Pleural Mesothelioma

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

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

Stage 4 Mesothelioma

Stage 4 Pleural Mesothelioma

In this stage, the cancer might be in the:

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

Peritoneal Mesothelioma Stages

Peritoneal mesothelioma staging involves a different system than pleural mesothelioma. This type of mesothelioma rarely involves metastasis to lymph nodes, so doctors don’t use that characteristic. They instead look at the extent of tumors in the abdominal cavity and follow the peritoneal mesothelioma staging system, also known as the PCI.

What Is the Peritoneal Cancer Index? Icon

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 Abdominal Cavity

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The PCI scores on a range of 0-39. The abdomen is divided into 13 sections, and each receives 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, it receives a 3. 

Some doctors simplify the PCI by correlating a score to one of the four 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 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 2021, she has survived for 13 years and counting.

Staging Systems

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

Mesothelioma TNM Staging Icon

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: tumor size (T), lymph node involvement (N) and metastasis (M). Each aspect receives a classification.


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 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 for lymph node involvement, 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 split stage 1 into 1A and 1B.

The Butchart System Icon

The Butchart System

Developed by Dr. Eric Butchart in 1976, the Butchart System is the oldest system for determining mesothelioma staging. It consists of four stages and focuses on the size of the tumors. It mostly ignores the number of tumors or the 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 in a mesothelioma case.

The system considers location, size and spread of the cancer. Stage 1 and stage 2 patients are candidates for surgery.

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 in a stage that prevents you from receiving curative treatment, then you should consider getting a second opinion. This may provide new treatment options to extend life. Get connected to a specialist today using our free Doctor Match program.

Frequently Asked 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.

Sources & Author

  1. Cancer Staging. American Cancer Society. Retrieved from: https://www.cancer.org/treatment/understanding-your-diagnosis/staging.html. Accessed: 04/06/2020.
  2. Malignant Mesothelioma Staging. American Cancer Society. Retrieved from: https://www.cancer.org/cancer/malignant-mesothelioma/detection-diagnosis-staging/staging.html. Accessed: 04/15/2020.
  3. Determining the Peritoneal Cancer Index. HIPEC.com. Retrieved from: http://www.hipec.com/knowledge-base/determining-the-peritoneal-cancer-index/. Accessed: 04/12/19.
  4. Malignant Mesothelioma Treatment (Adult). Vanderbilt-Ingram Cancer Center. Retrieved from: https://www.vicc.org/cancer-info/adult-malignant-mesothelioma. Accessed: 11/15/22.
  5. Contemporary Management of Malignant Pleural Mesothelioma. The Oncologist. Retrieved from: https://theoncologist.onlinelibrary.wiley.com/doi/10.1634/theoncologist.4-6-488. Accessed: 04/06/2020.
  6. In Memoriam: David J. Sugarbaker, MD (1953–2018). Texas Heart Institute Journal. Retrieved from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6379011/. Accessed: 04/06/2020.
  7. Presentation, initial evaluation, and prognosis of malignant pleural mesothelioma. UpToDate. Retrieved from: https://www.uptodate.com/contents/presentation-initial-evaluation-and-prognosis-of-malignant-pleural-mesothelioma#H16615464. Accessed: 04/06/2020.
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About the Writer, Karen Ritter, RN BSN

Karen Ritter, a registered nurse, is the lead patient advocate for Mesothelioma Guide. She has a deep passion for patient care, which includes helping patients and their families search for treatment options at the top mesothelioma cancer centers. She finds the balance between encouraging patients to receive the best treatment possible while enjoying their time with loved ones and friends. Karen is a valuable asset for patients due to her knowledge of mesothelioma, compassion for the victims of this disease and dedication to guiding patients through their treatment journey.