Mesothelioma is an aggressive form of cancer that occurs in a thin layer of tissue that covers most internal organs.
Malignant mesothelioma is a cancer of the thin layer of tissue that covers the heart, lungs and other internal organs. This tissue is called mesothelium; it protects organs by making fluid that allows, say, the lungs to move while breathing.
Mesothelioma is rare, with about 2,000 or 3,000 people in the United States getting a diagnosis each year, according to the American Cancer Society. Most people who contract it are over age 65.
The main risk factor for malignant mesothelioma is contact with asbestos. The tiny fibers of asbestos, when breathed, penetrate to the lining of the lungs. Symptoms typically show up 30 to 50 years after asbestos exposure, according to the National Cancer Institute.
It can be very difficult to treat, experts say.
This cancer is typically defined by the part of the mesothelium that is affected, Mayo Clinic researchers explain:
So-called epithelioid mesothelioma is the most common type and typically has a better prognosis than other types, the American Cancer Society states.
Symptoms include pain in the lower back or the side of the chest, shortness of breath, and trouble swallowing. A host of other symptoms range from cough and fever to belly pain and weight loss. Typically, malignant mesothelioma is not diagnosed until a patient visits a doctor with symptoms. No early diagnosis techniques currently are successful.
Surgery as a cure has been tried in rare cases where the patient is otherwise healthy, but often by the time it's diagnosed, malignant mesothelioma has spread to other organs, the Cancer Society notes.
Mesothelioma is also sometimes treated with radiation therapy or chemotherapy.
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