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Malignant mesothelioma is cancer that starts in the cells that line certain parts of the body, especially the chest and belly (abdomen). The lining formed by these cells is called mesothelium. These cells protect organs by making a special fluid that allows the organs to move. For instance, this fluid makes it easier for the lungs to move during breathing.

The mesothelium has different names in different parts of the body:

  • In the chest it is called the pleura.
  • In the belly it is called the peritoneum.
  • In the space around the heart it is called the pericardium.

Tumors of the mesothelium can be benign or they can be cancer. A cancer of the mesothelium is called a malignant mesothelioma, but this is often shortened to just mesothelioma.

The information that follows covers only those mesotheliomas that are cancer.

Types of mesothelioma

Mesotheliomas are grouped by where they start in the body.

  • Pleural mesotheliomas start in the chest. They account for about 3 out of 4 mesotheliomas.
  • Peritoneal mesotheliomas begin in the abdomen. They make up most of the remaining cases.
  • Pericardial mesotheliomas start in the covering around the heart and are very rare.
  • Mesotheliomas of the tunica vaginalis are very rare tumors that start in the layer around the testicles.

Mesotheliomas can also be grouped based on how the cancer cells look under a microscope.

  • Epithelioid: This is the most common type. It tends to have a better outlook (prognosis) than the other types.
  • Sarcomatoid (fibrous): About 1 to 2 out of 10 mesotheliomas are of this type.
  • Mixed (biphasic): This type has features of the 2 types above. About 3 to 4 out of 10 mesotheliomas are the mixed type.

Last Medical Review: 10/02/2012
Last Revised: 10/02/2012