The mesothelium is a membrane of tissue that is found throughout the chest and abdominal cavities, where it surrounds organs providing a protective layer. The pericardial mesothelium, also known as the pericardium, surrounds the heart. It is one of four areas of the mesothelium where asbestos caused cancer, or mesothelioma, has been known to occur. Pericardial mesothelioma is the development of malignant tumors on the tissue sac surrounding the heart.
Pericardial mesothelioma is the least common form of the disease. Five percent or less of mesothelioma cases are pericardial – this with a disease for which there are only about 3,000 new diagnoses in the U.S. every year. Part of the reason for its relative infrequency is the process through which mesothelioma develops.
The only known cause for malignant mesothelioma is asbestos. Specifically, the disease is caused when microscopic asbestos fibers lodge in the mesothelium tissue and eventually cause the development of inflammation and abnormal cells. The most common method by which asbestos fibers enter the body is through inhalation, which is why the most common form of the disease is pleural mesothelioma – a malignancy that develops in the outer lining of the lungs. How asbestos fibers travel to the pericardial mesothelium is not entirely clear. Speculation centers on the movement of these tiny fibers through the lymphatic system or through the cardiovascular system itself.
Impact of Asbestos Fibers on the Pericardium
Once asbestos fibers are lodged in the membranes surrounding the heart, they cannot be eliminated by the body. In fact, the body is incapable of shedding asbestos fibers naturally from any portion of the body. These fibers then begin to cause changes in the pericardial membrane, slowly over an extended period of time. As with other types of mesothelioma, the asbestos fibers cause thickening of the tissue layer which can result in chest pains similar to those affiliated with cardiovascular problems. Because heart disease is so common, pericardial mesothelioma may go undetected for some time due to a misdirected diagnosis.
The thickening of the pericardium often puts pressure on the four chambers of the heart, causing not only chest pain but restricted cardiovascular function. The result is often severe shortness of breath, a condition also associated with congestive heart failure. Another reported side effect is the occurrence of venal thrombosis, or clotting in the arteries – a dangerous occurrence in the major blood vessels attached to the heart.
While the exact nature of these changes is not completely understood, thickening of the pericardium eventually can lead to uncontrolled growth of cells in the pericardial layers, causing malignant mesothelioma tumors to form. As malignant cells grow in the pericardium, excess fluid develops in the area putting further pressure on the heart within the mesothelium sac.
Symptoms of Pericardial Mesothelioma
The rarity of pericardial mesothelioma has made it difficult for specialists to determine a specific set of common symptoms. The following symptoms often indicate a cardiac condition, but further tests are required to confirm a diagnosis of pericardial mesothelioma.
- Chest pain
- Irregular heartbeat
- Heart palpitations
- Shortness of breath
One of the unique features of mesothelioma in general is its extremely long latency period. The disease usually does not manifest itself for at least twenty years after the asbestos exposure has occurred, and often may not appear for forty years or more. People whose active work careers occurred from 1945 through 1980 and encountered asbestos are developing the disease in their retirement years, when heart ailments also usually manifest themselves.
Pericardial Mesothelioma Diagnosis
Diagnosis of pericardial mesothelioma is problematic, as the nature of these symptoms is relatively non-specific, in that they can appear as a result of several other cardiac conditions. Diagnosis will involve reviewing an individual's medical history as well as assessing their current medical condition.
Chest x-rays, a CT scan or an MRI scan may all be used to diagnose pericardial mesothelioma. However, to confirm the diagnosis and to determine whether the point of original of the cancer is the pericardium or another area, a biopsy must be performed. This involves removal of fluid or tissue from the pericardial area, and testing of this tissue or fluid for the presence of malignant mesothelioma cells. As with other forms of mesothelioma, medical imaging is usually inconclusive. Pericardial mesothelioma may take the form of a single tumor formed in conjunction with the effusion process – the accumulation of fluid – or it may take the form of a thickened and hardened mass involving the entire pericardial sac.
Treatment of Pericardial Mesothelioma
This form of mesothelioma differs from pleural or peritoneal mesothelioma because of the sensitivity of its location. As pericardial mesothelioma develops it directly impacts the function of the heart, to the point where emergency surgery can be necessary simply to relieve the pressure on the center of the cardiovascular system. An overly constricted heart can go into functional failure. Other forms of mesothelioma develop lethal characteristics more along the pattern of traditional cancer.
Unfortunately for most people who are diagnosed with pericardial mesothelioma, by the time symptoms of the disease appear, the cancer has progressed to a stage where conventional treatments are largely ineffective for anything other than providing temporary relief of symptoms. The difficulty of diagnosing pericardial mesothelioma at an early stage means that the long-term prognosis for most people with the disease is very poor. Survival time can range from mere weeks to fifteen months, but the average period is six months.
In rare cases, the disease may be diagnosed early enough that surgical procedures may provide some benefit. If pericardial tumors are small and have not spread to the lungs, chest wall or lymph nodes, radical surgery may successfully remove most cancerous tissue; however, such surgery is very risky due to the proximity of the heart.
For most people with pericardial mesothelioma, palliative treatment is the only option. This may include a procedure called fine needle aspiration, which removes excess fluid from the pericardium to relive pressure on the heart. Radiation therapy may be used to kill cancer cells and reduce the size of tumors, but this procedure is dangerous, as the heart and lungs themselves may be damaged. There have been reports of successful treatment using specific chemotherapy protocols with multiple drugs.
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- Triplet Chemotherapy for Malignant Pericardial Mesothelioma, Japanese Journal of Clinical Oncology, 2006