What Causes Mesothelioma?

The exact method by which asbestos causes mesothelioma isn’t known with certainty. Animal models have provided some understanding of the type of damage that asbestos fibers can do, but the exact mechanism hasn’t been found yet. After asbestos became a commercially successful product, it was soon apparent that asbestos workers were an at-risk population.

Starting at the turn of the century, British investigators discovered a relationship between exposure to high levels of asbestos and respiratory disease. These early studies were often suppressed by government at the request of the asbestos industry. By the mid 50’s American medical researchers had joined the chorus of concerned professionals identifying asbestos as hazardous. Much of their work was never published or was suppressed and/or disputed by scientists in the pay of the asbestos lobby.

Figure 3: Amphiboles Protruding, Brook T. Mossman, UVM College of Medicine.

Asbestos fibers have been detected in many resected surgical specimens from mesothelioma patients. In pleural mesothelioma, asbestos fibers are found trapped in the tissues from the lower parts of the lung and they are sometimes concentrated into nodules or spots on the parietal pleura, the primary location for mesothelioma in the thoracic cavity. These fibers are found using electron beam microscopy. They are invisible to the naked eye and are not routinely commented upon in a typical pathology report. Although smoking while exposed to asbestos is known to significantly increase lung cancer risks, smoking is not a risk factor in the formation of mesothelioma.  It is not uncommon to find pleural plaques in the lungs of patients with primary peritoneal mesothelioma which is indicative of heavy asbestos exposure.

Genetic susceptibility may also contribute to the cause of malignant mesothelioma. Populations of three small villages located in Turkey has been environmentally exposed to a rare asbestos-like fiber called erionite for generations.

50% of all deaths in these villages was attributable to malignant mesothelioma. All villagers lived in homes built with this mineral and research by Dr. Michele Carbone discovered that those who developed mesothelioma had a genetic predisposition  to the disease . Predisposed individuals who lived in villages without erinote were not found to develop mesothelioma. Further research into the residents of these communities has confirmed an autosomal dominant pattern of susceptibility to malignant mesothelioma and disease develops in the presence of asbestos-like fibers.

from : www.curemeso.org

What Is Mesothelioma?

Mesothelioma is a cancer of the smooth lining of the chest, lungs, heart, and abdomen. This skin layer is made up of mesothelial cells, hence the name mesothelioma. Mesothelioma is a diffuse but solid tumor that begins as a result of insult to the tissues caused by asbestos particles. These have penetrated into the pleural cavity of the chest or into the abdomen. Mesothelioma is either called pleural mesothelioma or peritoneal mesothelioma based on where it appears.

Because it occurs in such a small number of patients mesothelioma is often referred to as an orphan disease. Numbers of newly affected individuals in the United States have been reported to be between 2,500 and 3,000 every year. A steady rise in cases is reported in North America, Europe, Australia, and Asia.

In its early stages mesothelioma is difficult to detect as it may start with a thickening of the pleural rind, or fluid which can be associated with many other conditions. This rind is normally thin and smooth in the non diseased state. In time it begins to demonstrate progression forming a more pronounced irregular rind and nodules which coalesce into a crust that compresses and invades into adjacent structures compromising lung and cardiac function. In the abdominal cavity it can invade into the liver and bowel rendering the patient inoperable. Peritoneal mesothelioma it is often found coating the omentum described sometimes as a salt like sand like particles too numerous to count and impossible to remove without sacrificing the entire omentum. Involvement of the ovaries and fallopian tubes is not uncommon in women and often mesothelioma is confused with ovarian cancer. Once vital organs are involved or disease identified outside of the operative field surgery is no longer an option and patients are referred to chemotherapy or clinical trials.

Figure 1: Right Pleural Epithelial Mesothelioma on chest wall and lung. Photo courtesy K. Brauch

For the vast majority of patients, as the tumor mass grows, once subtle symptoms will give way to weight loss, cough, respiratory infections, fatigue, shortness of breath, digestive and bowel problems and pain in the chest or abdomen, depending upon whether it is pleural or peritoneal. It may begin to weep fluid into the intracavitary space. In the chest cavity this is called an effusion and it fills the space where the lobes of the lung reside, next to the lining of the chest cavity, and often spreads into the area surrounding the heart creating symptoms similar to those observed in congestive heart failure. In peritoneal patients it is called ascites and it fills the abdomen bathing the visceral organs with this malignant fluid.

Figure 2: Epithelial mesothelioma on the diaphragm. Photo courtesy K. Brauch.

The symptoms gradually become more noticeable prompting the patient to seek a medical consultation. By this time the progression of the disease may already be too advanced as the tumor may have spread to the lymph nodes and/or begun to metastasize to remote organs of the body like the brain, spleen, liver or kidneys. Metastatic mesothelioma is considered late stage and incurable, given the current state of treatments. It is widely reported that only 10-20% of patients with pleural mesothelioma are diagnosed early enough for surgical intervention, the rest are referred on to palliative care No such figures have been reported in peritoneal mesothelioma.