Is Mesothelioma Always Malignant?

Malignant mesothelioma is a form of cancer that affects the mesothelium, which is the lining of tissue that surrounds several vital organs. The organ tissues most likely to be affected by mesothelioma generally surround the lungs, heart, and abdomen. Very rarely, the tunica vaginalis or lining surrounding the testicles can also be affected.

Asbestos and Malignant Mesothelioma

The majority of tumors associated with mesothelioma are considered malignant, meaning that they are cancerous and have the ability to spread to other organ systems. While benign tumors can be located in the mesothelium, nearly all resulting from asbestos exposure are malignant.

Asbestos is a hazardous, naturally occurring mineral that is extremely friable and resistant to heat. Once the small particles that compose asbestos break apart they become airborne where they are easily inhaled or ingested. Inside the body, these fibers embed themselves in the aforementioned tissues, acting as a human carcinogen.

Classifications of Malignant Mesothelioma

Malignant mesothelioma is classified as being one of four types:

  • Epitheliod—makes up approximately 50 to 60 percent of mesothelioma, and presents a more favorable prognosis than the others.
  • Sarcomatoid—10 to 20 percent of mesotheliomas are this type.
  • Biphasic (or mixed)—mesothelioma found in both epitheliod and sarcomatoid areas, makes up approximately 30 to 40 percent of mesothelioma cases.
  • Desmoplastic—extremely rare.

Along with type, mesothelioma is also classified according to the four main areas in the body in which the cancer originates:

  • Pleural mesothelioma—this form of mesothelioma begins in the chest and currently accounts for approximately three out of four cases of mesothelioma.
  • Peritoneal mesothelioma—this is the second most common form of mesothelioma and begins in the abdomen.
  • Pericardial mesothelioma—a more rare form of mesothelioma, pericardial refers to the covering surrounding the heart.
  • Mesothelioma of the tunica vaginalis—these extremely rare tumors begin in the covering layer of the testicles, which, according to the American Cancer Society, is an outpouching of peritoneum.

Malignant mesothelioma demonstrates extremely long latency periods, meaning the cancer lies dormant within the body for an extended period of time before symptoms begin to show. Early symptoms of the disease, such as cough, shortness of breath, and pain in the lower back or at the side of the chest, are often mistaken for common ailments and illnesses. It is common for those with mesothelioma to not be diagnosed until the cancer has progressed into the later stages; a major reason for the cancer’s reduced survival rates.