Pericardial mesothelioma is a very rare cancerous disease of the tissue layers surrounding the heart. The mesothelium membrane is comprised of two layers, one that adheres to a moving internal organ such as the heart or lungs, and the other which forms a sac around the organ. The tissues secrete a lubricant that allows the active organ to move easily against adjacent structures, such as the rib cage and diaphragm. The peritoneum is the mesothelial layer that lines the abdominal cavity, the pleura lines the chest cavity, and the pericardium surrounds the heart. Abnormal growth (cancer) in the cells of any of these mesothelial structures is referred to as mesothelioma.
The primary cause of mesothelioma (in 70 to 80% of diagnosed cases) is exposure to asbestos in the workplace, even for brief periods, with symptoms sometimes taking up to 50 years after exposure to become apparent. Among the populations most effected by mesothelioma are miners who were employed in South Africa and Australia (including a large number of Italian immigrants), who often worked in dusty conditions without protective equipment. Among Americans and Europeans, most cases have arisen among those who worked with asbestos in the construction trades and shipbuilding, where asbestos was used extensively for its insulating properties and as a fire retardant. Generous financial settlements have been forthcoming as the result of lawsuits initiated by effected workers. At this point, however, there is insufficient evidence to link pericardial mesothelioma to asbestos exposure. Similarly, smoking does not appear to be a risk factor for mesothelioma.
Only one to five percent of mesothelioma cases can be classified as primary pericardial mesothelioma – primary implying that they originate in the pericardium. The majority of cases (60 to 70%) are pleural, and the remaining cases (30 to 35%) are peritoneal. Cancers originating in the pleura or peritoneum can spread to include other areas of the body, including the pericardium. The disease occurs across all age groups, almost equally in both sexes. With the elimination of asbestos in many building products and an overall improvement in working conditions and health monitoring, it is likely that the overall incidence of mesothelioma will decline in the next decade or so. In the absence of the identification of a principle causative agent, it is less clear whether the incidence rate of primary pericardial mesothelioma will change.
Results from an extensive study of autopsy records from 500,000 people who had died from cancer showed that primary tumors of the pericardium were responsible in only 0.0022% of the cases. With respect to all pericardial and cardiac primary tumors, only 2 or 3 percent are associated with mesothelioma, well behind the numbers for angiosarcoma (33%) and rabdomyosarcoma (20%).
Among the cases of pericardial mesothelioma described in the medical literature, men of ages 29, 44, 68, and 70 reported a range of symptoms including shortness of breath, night sweating, chest pain associated with exertion, persistent cough, general malaise and some swelling of the face and upper extremities. These symptoms are common to other forms of mesothelioma and to a number of other conditions affecting the heart and lungs, such as pneumonia and lung cancer. In many cases, symptoms are not apparent until the disease has progressed to advanced stages, leaving few options for effective treatment.
Diagnosis of pericardial mesothelioma often takes place when the disease is quite advanced, at a point when the tumor and associated swelling are constricting other thoracic structures such as veins, arteries and airways. Pericardial swelling can also be associated with tuberculosis, rheumatoid arthritis, and other conditions.
Radiography and other imaging techniques (e.g., echocardiography and magnetic resonance angiography) can be used to demonstrate swelling of the pericardium. In some cases, the myocardium and coronary arteries might also be involved. Isotope scans with gallium or technetium as well as cardiac catheterization can be used to measure decreased function in the heart and blood vessels. Post-contrast computerized tomography can be used to differentiate the tumor mass from the rest of the swollen tissue surrounding the heart. However, even with the identification of a tumor, the use of imaging techniques alone will not result in a definitive diagnosis because melanoma, leukemia and lymphoma can also involve the pericardium. Precise diagnosis requires demonstrating that the tumor has no relationship with the pleural surfaces.
Standard laboratory tests of blood, urine, and sputum are of little help in detecting mesothelioma. Liquid extracted from the swollen area can provide adequate cytological evidence for accurate diagnosis, but in some cases this method has resulted in a misdiagnosis, indicating other cancers (e.g., adenocarcinoma).
A biopsy carried out on a tissue sample obtained by thoracoscopy or sternoscopy is the only way to substantiate a positive identification of mesothelioma. In terms of specific laboratory indicators for the presence of mesothelioma, the cancer cells stain positive for cytokeratin, vimentin, epithelial membrane antigen, and calretinin and negative for CEA, CD15, CD34 and S-100. In 60 to 80 percent of cases, accurate diagnosis based on histological analysis of tissue samples is only accomplished after the death of the patient.
The choice of treatment regimen is dependent on how far the cancer has progressed at the time a positive diagnosis is made, and isl also be based on the age, weight, medical history, and general well-being of the individual concerned.
With early detection, when the tumor mass is small and localized, radical surgery for removal of cancerous tissue is possible but risky, given the proximity to the heart and lungs. If the cancer has spread to the lymph nodes, lungs, chest wall, or other organs (as it does in 25 to 45 percent of cases), surgical removal is no longer an option.
A course of palliative surgery for draining fluid from the pericardium,
as a means of relieving pressure on proximal structures, can be used to
alleviate symptoms and as a way to obtain a tissue sample for biopsy.
This procedure can be used to help prolong life while other treatment
modalities are administered.
Radiation therapy can be used to kill the cancer cells and shrink tumors, but this approach carries with it the risk of damaging the heart and lungs. As well as the more familiar practice of external exposure to radioactive materials, treatment might involve delivering radioactive materials directly to the cancer site through plastic tubing (internal therapy).
At this point, no chemotherapeutic agents have been shown to be effective in the treatment of pericardial mesothelioma.
As a direct consequence of the difficulties in definitively diagnosing pericardial mesothelioma and the fact that it usually only minimally symptomatic until its advanced stages, the prognosis for patients is very poor, with a mean survival time of only six months following diagnosis. Death often occurs as the result of congestive heart failure or occlusion of the superior vena cava. This situation is unlikely to change without significant advances in early detection techniques and treatment regimens.
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