Why is mesothelioma so rare?
Mesothelioma is a rare type of lung cancer. It is the only form of lung cancer not caused by smoking. The only known cause of mesothelioma is asbestos, which many Americans have been exposed to in the home or in the workplace. Mesothelioma is the only form of lung cancer not caused by cigarette smoke.
Mesothelioma also has a long latency period, which means that it develops long after exposure to asbestos. Some mesothelioma cases are not diagnosed until fifty years after the patient’s first asbestos exposure.
About 2,000 mesothelioma cases are diagnosed every year in the United States. Because the US did not take legal action against asbestos until the 1970’s and mesothelioma has a long latency period, the number of mesothelioma cases in the US is expected to increase in coming years. This makes mesothelioma research more important now than ever.
Mesothelioma forms in the lining of a patient’s internal organs, or mesothelium. The mesothelium has two layers with fluid between the layers. This allows organs like the lungs to move freely during breathing and other normal processes. When cells in the mesothelium become cancerous, they grow rapidly and randomly. This results in a tumor, which presses down on the organs and interferes with their normal functions.
The pleura, or lining of the lungs, is the most common site for mesothelioma to develop. Mesothelioma in the lining of the lungs is called pleural mesothelioma, and it affects most mesothelioma patients. Pleural mesothelioma is usually confined to the right lung, but can spread to the lymph nodes in the chest and then to other parts of the body, which is called metastasizing.
Mesothelioma can also form in the lining of the abdomen. Mesothelioma affecting the abdominal lining, or peritoneum, is called peritoneal mesothelioma. Peritoneal mesothelioma is treated with the same chemotherapy drugs as pleural mesothelioma, and the outcomes are similar for both peritoneal and pleural mesothelioma.
Pericardial Mesothelioma occurs in the pericardium, or lining of the heart. It is very rare, and it is unclear how asbestos fibers cause mesothelioma in the pericardium. Symptoms are similar to many other heart diseases, and usually involve chest pain, heartbeat irregularities, and exhaustion. Pericardial mesothelioma is particularly difficult to treat because the tumor is so close to the heart that removing the tumor by surgery is extremely risky.
Testicular mesothelioma, or mesothelioma of the tunica vaginalis (the lining of the testicles), is the rarest form of mesothelioma. Testicular mesothelioma can either spread from peritoneal mesothelioma or develop on its own. In cases where testicular mesothelioma is confined to the lining of the testicles, treatment is relatively straightforward because surgery for testicular mesothelioma is less invasive than peritoneal or pleural surgeries.
Malignant vs. Benign
Mesothelioma can be malignant or benign. Benign mesothelioma is a tumor that is not actively growing. This means it is not cancerous and is less of a threat to the patient’s health. Benign mesothelioma can be removed with one surgery and does not grow back afterwards.
Malignant mesothelioma is an aggressive cancer: “malignant” means that it invades healthy tissue. Malignant mesothelioma is difficult to treat and eventually fatal if not controlled. The bulk of this site discusses malignant mesothelioma, as malignant mesothelioma is more common and dangerous than benign mesothelioma.