What is Mesothelioma?

Mesothelioma is a type of cancer, usually in the lining of the lung - the pleura.

More than 90% of mesotheliomas are caused by asbestos.

Mesothelioma can be caused by short periods of exposure to asbestos. You might not have worked with asbestos. People who lived near asbestos factories have developed mesothelioma. Women have developed mesothelioma as a result of washing their husbands' or parents' contaminated work clothes.

The risk of developing mesothelioma depends on the dose of asbestos breathed in over your lifetime. The risk increases with the dose. A thermal insulation engineer or lagger will have had the heaviest type of exposure to all 3 main types of asbestos: blue, brown and white. He has a 1 in 10 risk of developing mesothelioma. But a car mechanic, who blew out brake drums, has a very much lower risk of developing mesothelioma.

The risk is higher the heavier your exposure has been to blue or brown asbestos, but all asbestos is dangerous.

To have caused the disease, the asbestos dust is likely to have been been breathed in at least 10 years before symptoms develop. Dust may have been inhaled as long as 50 or 60 years ago before mesothelioma develops. The average period between first exposure to asbestos and developing the disease is 30-40 years.

Most people who develop mesothelioma do not have asbestosis.

Mesothelioma is not caused by cigarette smoking.

In Britain, more than 2,000 people die each year from mesothelioma. This epidemic will peak within the next 5 to10 years. Even after that, there will be thousands more victims.

In most cases, mesothelioma develops in the pleura. The pleura is the lining between your lung and your rib cage. It has two layers, like an envelope.

Mesothelioma can sometimes develop in your peritoneum, the lining between your bowel and the cavity of your abdomen. Rarely, mesothelioma may attack other parts of the body, such as the lining of the heart (the pericardium).

Very small fibres of asbestos, so small that you cannot see them, are breathed in and penetrate the lungs down to the smallest airways. Some of these fibres reach the lining of the lungs, the pleura. The body has defence mechanisms that surround or expel fibres. But at some point, the defence mechanisms are overwhelmed, and the process of tumour development begins. It is not understood fully why or how this happens.

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. Epithelioid mesothelioma is the most common type.

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 whereby 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 often 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.

If someone dies of mesothelioma, there should be an inquest. The coroner must be told immediately, and there will usually be a post-mortem.

Copyright © Anthony Coombs 2006