Mesothelioma is a rare form of cancer that develops in the mesothelial cells. These cells are tissue that surround or line the lungs, heart, and stomach. The mesothelial cells protect these organs by producing a lubricating fluid that allows these organs to move smoothly.
There are 2 types of tumors of the mesothelium, “benign” and “malignant”. A benign tumor is non-cancerous, which means it does not cause any damage or will not harm you. A malignant tumor of the mesothelial cells is called a malignant mesothelioma. Because tumors of the mesothelium are usually cancerous, malignant mesothelioma is usually just called “mesothelioma”.
Malignant mesotheliomas arise from the cells that line the surface of the pleura or the peritoneum. Eighty percent of these tumors are pleural in origin. Malignant mesotheliomas are rare, with an incidence of one to three cases per 1 million persons per year in the general population.
The relationship between asbestos exposure and malignant mesothelioma was established in 1960. The latency period between exposure and tumor development has usually been 30 years or more.
The incidence of malignant mesothelioma has been highest in persons with heavy occupational exposure to asbestos, such as shipyard workers. However, malignant mesothelioma can occur in the absence of any known asbestos exposure. No history of such exposure has been noted in about one-third of cases, and the etiology of these cases is unknown. Cigarette smoking is not considered a risk factor for malignant mesothelioma.
The patient with malignant mesothelioma of the pleura may have symptoms of dyspnea and pleuritic chest pain, with malaise and weight loss. A large pleural effusion is often seen on the radiograph. This effusion is frequently bloody, and the hyaluronic acid level may be elevated. Associated parenchymal fibrosis (asbestosis) is rare in pleural mesothelioma but appears to be more common in, peritoneal mesothelioma.
Malignant mesothelioma can be very difficult to diagnose; open biopsy is usually necessary, because needle biopsy of the pleura often yields an inadequate specimen.
There is no effective treatment for malignant mesothelioma. Surgical resection is not possible. The tumor encases the lung in a bulky, lobulated mass that invades the fissures and, eventually, the diaphragm and the chest wall. Average survival is less than two years. Except in rare cases, chemotherapy and radiation therapy have not been useful.
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