The time from exposure to the development of the disease and its symptoms is very long. Usually it is 30-40 years after exposure before the disease develops. For this reason connecting the symptoms to the cause of the disease can be difficult. Additionally, once these symptoms develop, many are nonspecific and very similar to other more common diagnoses making it difficult to correctly identify the patients diagnosis. This means that the correct treatment is often delayed. These factors contribute to the poor prognosis often associated with this disease.
The average survival once the diagnosis is made averages a year or less. At experienced centers involved in clinical trials this rate is higher and in certain cases approaches a 40% five year survival rate. Early diagnosis and treatment is essential to long term survival.
Treatment is guided by the type, location and extent of involvement of the disease as well as the patients overall health.
The approach to treatment includes several options; surgery, radiation and chemotherapy, used singly or in combination.
Surgery such involves removing the tumor or affected tissue. This can be limited by the size and location of areas affected. Radiation treatment in mesothelioma is done by placing radioactive sources in the affected tissue and leaving it for a period of time to continue to kill off abnormal cells. Chemotherapy in the form of pills or injected medication is used. However this therapy is not specifically targeted to the mesothelioma and can have significant side effects.
In cases where the disease is far advanced and a cure is not felt to be likely, these treatments can still be used for palliative therapy to improve quality of life and keep the patient comfortable.
Mesothelioma occurs in the lining of the lungs (pleura), abdominal (peritoneum) and heart (pericardium). Its occurrence is greatest in the lungs with about two-thirds of all cases. The abdomen accounts for 20-30% of cases. Involvement of the pericardium or reproductive organs is rare. Unlike other forms of cancer that form a lump, mass or tumor mesothelioma spreads sheet like along the surface of the pleura or peritoneum and then extends into the tissue it surrounds.
Another aspect of mesothelioma is the hardening of the mesothelioma tissue that then forms a case like structure around the organs involved. In the case of pleural mesothelioma this would then restrict movement of the lungs making it difficult for an individual to take a deep breath. It does metastasize like other types of cancer but this usually occurs only after localized involvement is extensive.
Symptoms are related to the location and extent of involvement. In pleural mesothelioma, the most frequently occurring symptoms are shortness of breath, chest pain, persistent cough. These symptoms are a result of a pleural effusion that results from fluid collection between the lung and the lung lining which is now compromised by mesothelioma.
If the less common peritoneal mesothelioma occurs there will be abdominal pain, weakness, weight loss, nausea and loss off appetite. Again location and the pattern of involvement determine symptoms displayed which can include abdominal swelling and bowel obstruction. If the peritoneum or organs under the diaphragm is involved difficulty breathing can also be experienced without lung involvement.
In the rare case of pericardial sac involvement symptoms are chest pain, persistent cough and palpitations. Due to restrictions of cardiac filling caused by invading tumor patients can experience shortness of breath.
Mesothelioma is a rare form of cancer that develops in the mesothelial lining of the lungs (pleura), abdominal (peritoneum) and heart (pericardium). It is caused by exposure to asbestos that is ingested or inhaled. Asbestos material is used in acoustical materials, floor tiles, brake linings and fire retardant materials. Invisible fibers are released when the material is disturbed, torn or damaged. The small size of these fibers mean that visual inspection does not rule out environmental contamination.
Removal or repair of asbestos requires experienced professionals and significant environmental controls. Professions commonly exposed to asbestos include engineers, pipefitters, steel workers and auto mechanics. The greater the amount of exposure to asbestos fibers, the greater the risk. Smoking synergistically increases the risk of developing pulmonary mesothelioma.
Differentiation of mesothelioma from bronchogenic carcinoma is necessary to determine the optimal treatment strategy, and often requires histologic and/or histochemical examination of tissue samples collected by tumor biopsy. Mesothelioma can be primarily sarcomatoid or epithelial, and the epithelial type histology resembles that of bronchogenic adenocarcinoma. Acid mucopolysaccharide-positive, perinuclear keratin-positive, and CEA/Leu-M1-negative samples favor diagnosis of mesothelioma over adenocarcinoma. Clinical and radiologic presentation as well as gross appearance of the different tumor types can be markedly similar. While smoking history has a different impact on the risk for development of mesothelioma versus bronchogenic carcinoma, it is not helpful in distinguishing the two entities clinically.
50%. Excepting the case of stage I disease (a localized, non-invasive lesion), which can often be completely surgically resected, mesothelioma is usually fatal eventually, even with the best available treatment. Treatment strategy will depend on the location, size, and staging of the individual tumor and can include surgery (wedge resection, lobectomy, or pneumonectomy), chemotherapy, radiation, and photodynamic therapy (a chemically-targeted laser therapy). Numerous clinical trials are currently ongoing, which seek to improve survival rates for established therapeutic modalities (especially chemotherapy).
While smoking greatly increases the likelihood of asbestos-related bronchogenic carcinoma, it is not associated with an increased risk of mesothelioma. Approximately 90% of cases of malignant pulmonary mesothelioma are asbestos-related, and there is a positive correlation between length of exposure and development of disease. Note that while age is not a direct risk factor, time elapsed since asbestos exposure is, since the delay between exposure and onset of disease is typically 25-45 years. Thus, a younger patient is less likely to have had sufficient time since asbestos exposure for the development of mesothelioma.
While advanced invasive mesothelioma, or mesothelioma with associated asbestosis (present in only 20% of cases), might present with hemoptysis, the clinical finding of hemoptysis is more suggestive of an airway lesion than mesothelioma, which arises from the pleura. Pleural membranes line the thoracic wall, lung, and mediastinum, and thus have no direct connection with the airway before the anatomy is deranged by the disease process. Dyspnea, pleural effusion, productive cough, and chest pain can all result from the primary lesion of mesothelioma, which is typically a localized or diffuse thick malignant tissue on the thoracic surface of the lung which can aggravate the pleura (leading to chest pain and/or pleural effusion), and produce a mass effect on the lung (leading to dyspnea).
While the large majority of malignant mesotheliomas are pulmonary (i.e. of pleural origin), the tumor can also arise from cells of the peritoneum, pericardium, and tunica vaginalis of the testis. Mesothelial cells form the serosa which line the thoracic and abdominal cavities. They also contribute to the pericardium and the tunica vaginalis which surround the heart and testis, respectively. They are derived from embryonic mesoderm. Note that bronchiolar epithelium derives from endoderm, not mesoderm; and myocardial tissue, while mesodermal in origin, does not contain mesothelium. Most cases of malignant mesothelioma are associated with past history of asbestos exposure. Note that benign mesothelioma IS NOT associated with asbestos exposure.