What is Mesothelioma?
Mesothelioma is an incurable and extremely painful malignancy of the outer lining of the lung (the pleura) or the lining of the abdominal cavity (the peritoneum). The bulk of mesotheliomas affect the pleura. As the disease progresses the pleura or the peritoneum thickens from the thickness of cigarette paper to form a hard tumour mass between 0.5cm and 1cm thick. This mass encloses and compresses the lung, in the case of pleural mesothelioma, and the intestines in the case of peritoneal mesothelioma, to the point of collapse.
Cause of Mesothelioma
Asbestos exposure is the only known cause of mesothelioma in Australia. There is no link between cigarette smoking and mesothelioma. The only other known cause of mesothelioma is erionite, a fibrous mineral found in Turkey. Mesothelioma is the most lethal of all asbestos disease.
Mesothelioma can be caused by very short periods of exposure to asbestos. People have developed mesothelioma from working with asbestos materials for only a couple of hours, from living near a factory which manufactured asbestos materials or from the clothes of their spouse or parent. However, it is a very rare cancer and even those people with high exposures to asbestos do not usually develop the disease.
There is generally a latency period of 15 to 60 years between the exposure to asbestos and the development of the disease. Indeed, experts will generally not associate an exposure to asbestos that has occurred within the last ten years to the development of mesothelioma.
Types of mesothelioma
There are different types of mesothelioma: epithelioid, sarcomatous, and biphasic (a mixture of the first two). The speed at which the disease develops often depends upon which type of mesothelioma it is.
Mesothelioma generally occurs in the pleura, although sometimes occurs in the peritoneal cavity.
Symptoms & diagnosis
Symptoms of pleural mesothelioma usually begin with breathlessness, or with back or chest pain, caused by a build up of fluid between the two layers of the pleura surrounding the lung. This build up of fluid is called a pleural effusion. This fluid usually has to be drained from the pleural space to relieve the pressure on the lung. The fluid is then tested. This is called cytology. This alone does not usually prove that mesothelioma is present.
Mesothelioma can be difficult to diagnose. There are other causes of pleural thickening and fluid around the lining of the lung. These conditions can be caused by other cancers, or by infections, or persistent inflammation.
A biopsy, sometimes more than one biopsy, has to be done in order to diagnose mesothelioma. A biopsy involves removing and analysing very small pieces of tissue from the pleura.
There are different types of biopsy: needle biopsy, a needle biopsy guided by CT scan or ultrasound, video assisted thoracoscopic biopsy, in which the surgeon looks into the chest through a telescope and takes samples, and an open biopsy where the surgeon opens the chest cavity and takes samples under direct vision. The pathologist looks at the tissue under the microscope and performs special tests on the tissue to diagnose mesothelioma.
It can sometimes take weeks, or even months, for doctors to diagnose mesothelioma with certainty.
Patients sometimes develop swelling and discomfort at the wound sites where biopsies have been carried out, or surgery performed. Radiotherapy is sometimes used to prevent the tumour spreading in this way and to treat these symptoms if they occur.
In mesothelioma of the lining of the abdomen (peritoneal mesothelioma), patients have swelling of the abdomen resulting from fluid that accumulates. This fluid is called ascites.
People who die of mesothelioma usually die from complications of the disease in the place it originated, usually the chest, and not from its spread to other parts of the body. The fluid that begins in the pleura is eventually replaced by solid tumour that can cause difficulty breathing, pneumonia or heart problems as well as pain that requires medication itself.