What is mesothelioma?

Last medical review:

Mesothelioma is a type of cancer that starts in cells of the mesothelium. The mesothelium is the membrane that lines cavities in the body and surrounds most of your internal organs.

The mesothelium has different names depending on where it is in the body. The mesothelium that lines the chest wall and surrounds each lung is called the pleura. The mesothelium that lines the abdominal wall and pelvis and covers the organs in the abdomen and pelvis is called the peritoneum.

The mesothelium is made up of mesothelial cells. These cells sometimes change and no longer behave or grow normally. These changes may lead to non-cancerous (benign) tumours, such as a fibrous tumour of the pleura. But in some cases, changes to mesothelial cells can cause mesothelioma.

Mesothelioma is a very rare type of cancer. It usually starts in the pleura, which is called pleural mesothelioma. This type of cancer makes up 75% to 80% of all mesotheliomas.

Cancer can also start in the peritoneum, which is called peritoneal mesothelioma. This type of cancer makes up about 8% of all mesotheliomas.

Even rarer types of mesothelioma can also develop. Pericardial mesothelioma starts in the membrane that surrounds the heart. Tunica vaginalis starts in the membrane that surrounds each testicle.

Expert review and references

  • John Cho, MD, PhD, FRCPC
  • American Cancer Society. Malignant Mesothelioma. 2018. https://www.cancer.org/.
  • Pass H, Carbone M, Tsao A, Rosenzweig Z. Benign and Malignant Mesothelioma. DeVita VT Jr, Lawrence TS, Rosenberg S. eds. DeVita Hellman and Rosenberg's Cancer: Principles and Practice of Oncology. 12th ed. Philadelphia, PA: Wolters Kluwer; 2023: Kindle version, [chapter 76], https://read.amazon.ca/?asin=B0BG3DPT4Q&language=en-CA.
  • National Comprehensive Cancer Network. NCCN Guidelines for Patients: Pleural Mesothelioma. 2022.
  • Nowak AK, Edwards JG, Creaney J. Mesothelioma. Raghavan D, Ahluwalia MS, Blanke CD, et al, eds.. Textbook of Uncommon Cancer. 5th ed. Hoboken, NJ: Wiley Blackwell; 2017: Kindle version (chapter 16) https://read.amazon.ca/?asin=B06XKD44V3&_encoding=UTF8&ref=dbs_p_ebk_r00_pbcb_rnvc00.
  • Sauter JL, Dacic S, Galateau-Salle F, et al. The 2021 WHO Classification of Tumors of the Pleura: Advances Since the 2015 Classification. Journal of Thoracic Oncology. 2022: 17(5):608–622.

The mesothelium

Mesothelioma starts in the mesothelium. It is the membrane that lines cavities in the body and surrounds and cushions different organs.

Types of mesothelioma

Mesothelioma is a rare type of cancer. Pleural mesothelioma develops more often than peritoneal mesothelioma. There are also very rare types of mesothelioma.

Non-cancerous tumours of the mesothelium

Fibrous tumour of the pleura is the most common non-cancerous tumour of the mesothelium.

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