Malignant Mesothelioma (“MEEZ-O-thee-lee-O-ma”) is a rare cancer that originates in the cells lining certain parts of the body, particularly the chest (pleura) or abdomen (peritoneum). These cells, mesothelial cells, form a lining called the mesothelium, which helps protect your organs by making a lubricating fluid, allowing ease of movement, such as the lungs during breathing.
About 80-90 percent of Malignant Mesothelioma cases start in the pleura.
Peritoneal Mesotheliomas make up most of the rest. Very rarely, Malignant Mesotheliomas start in the lining of the heart (pericardium) or testicles (tunica vaginalis).
Malignant mesothelioma is a rare cancer. In the US, there are only about 2,000-3,000 new cases diagnosed annually (compared to about 200,000 cases of lung cancer each year). Worldwide, the incidence appears to be on the increase. Malignant mesothelioma is usually a disease of the elderly, with the vast majority occurring in those over 65.
Causes of Malignant Mesothelioma: A risk factor is something that affects your chances of getting a disease, but does not mean that you will get the disease. Risk factors for Malignant Mesothelioma include asbestos, zeolites (such as erionite, a mineral found in the soil in parts of Turkey), radiation (high doses used in the past for certain cancers), thorium dioxide injections (“Thorotrast”) used for certain x-ray tests until the 1950s, and possibly SV40 virus (a simian virus that contaminated some vaccines about 50 years ago). Unlike lung cancer, smoking cigarettes does not cause Mesothelioma.
In the US, the main cause of Malignant Mesothelioma is asbestos. After someone breaths in the asbestos fibers, they can travel to the mesothelial cells and cause DNA damage that result in cancerous growth.
Most cases of Malignant Mesothelioma involve workplace asbestos exposure, but household or environmental exposure can cause this disease. The risk of Malignant Mesothelioma increases with increasing asbestos dose (“dose-response”), but even very small doses can cause this cancer. Malignant Mesothelioma takes a very long time to develop, with time between first exposure to asbestos and diagnosis (“latency period”) often 20-50 years, or longer (even if exposure stopped long ago).
Types of Malignant Mesothelioma: There are three different types of Malignant Mesothelioma, based upon how the tumor cells are arranged when examined under a microscope: Epithelioid, Sarcomatoid (Fibrous), or Biphasic (Mixed). The Epithelioid type have the better prognosis and comprise about 50-60% of Malignant Mesotheliomas.
What are the signs and symptoms of Malignant Mesothelioma? The symptoms, especially early on, are non-specific (could be from other reasons) and many people wait months before seeking a doctor. Depending upon where the cancer arises, signs and symptoms include: unexplained weight loss, chest or abdominal (belly) pain, shortness of breath, fatigue, cough, fluid around the lungs, nausea, or swelling or fluid in the abdomen.
How is Malignant Mesothelioma diagnosed? If you develop signs or symptoms of Malignant Mesothelioma, go see your doctor. He or she will take a thorough history, including any exposures to asbestos, and perform a complete physical examination. If your doctor still suspects Mesothelioma, you will likely undergo further testing, including blood tests, x-rays, scans, and other procedures. Your regular doctor may refer you to a lung specialist (pulmonologist).
Chest x-ray or chest CT scan can reveal thickening of the chest lining and the accumulation of fluid in the pleural space. There may also be evidence of previous asbestos exposure, such as pleural plaques, pleural calcification, or asbestosis.
Other imaging techniques used include Positron Emission Tomography (PET scan), Magnetic Resonance Imaging (MRI), or Abdominal CT.
Blood tests, in addition to commonly ordered tests like Complete Blood Count (CBC), electrolytes, kidney function, or liver function tests, might include osteopontin or soluble mesothelin-related peptides (SMRPs).
Other testing might include Pulmonary Function Tests (PFTs), bronchoscopy (insertion of a scope into the lungs), thoracentesis or paracentesis (removal of fluid from the chest or abdomen) or closed pleural biopsy (taking a piece of tissue through a needle). More often, your doctor will send you to a surgeon for biopsy through a scope (thoracoscopy, mediastinoscopy, or laparoscopy), or surgical open biopsy.
The diagnosis of Malignant Mesothelioma is then confirmed by the pathologist who examines the fluid or tissue using a microscope and specialized lab tests. Sometimes the pathologist needs more fluid or tissue before confirming the diagnosis.
Treatment Decisions: After your doctor diagnoses Mesothelioma, he/she will discuss treatment options. This might involve other physicians, such as a cancer specialist (oncologist), thoracic (chest) surgeon, or radiation specialist. Unfortunately, this cancer is almost always incurable. Without treatment, the mean survival is about 9 months. Treated, survival time could double. Your age, general health, type of cancer, and spread of cancer affect your prognosis.
Most cases are not surgically removable and not many patients are able to tolerate the surgery. Combination chemotherapy seems to prolong survival but is not a cure. Radiation may reduce symptoms. Consider participation in a clinical trial, particularly at a major cancer center. Current research includes gene therapy, new targeting chemotherapy, multimodality treatment, photodynamic therapy, and new radiation therapy techniques.
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