How is Mesothelioma Diagnosed?

Mesothelioma is almost always caused by exposure to asbestos, and that could have been 20 years ago, or 30 or even 50 years ago. It takes all those years for the tiny asbestos fibers to work their way deeply into the pleura, the membrane around the lungs. They may even penetrate all the way to the air sacs, where oxygen and carbon dioxide are exchanged.

In a minority of cases, the fibers work their way into the pericardium, the membrane around the heart. If the asbestos was ingested (from air-borne fibers getting into food) they will work their way into the peritoneum, the abdominal cavity membrane. Or alternatively, the fibers may travel to the abdomen from the lung area in the lymphatic system.

Immune System Failure

Once those fibers are in the mesothelium, the body cannot get rid of them. Normally, when there are any cells the body regards as “foreign”, such as a flu virus, special defense cells rush to the site and attempt to engulf it. They are called macrophages and are part of the body’s immune system. They will usually carry the “foreigner” away in the bloodstream to be excreted. (Of course, the effectiveness of this reaction varies from person to person.)

When macrophages rush to engulf asbestos fibers, they have met their match. Asbestos was used so widely for so many decades because it has several remarkable properties. It is a flame-retardant, blocks sound, and does not conduct electricity. And it resists chemical change. It defeats the macrophages, which die in the battle and accumulate in the area as debris, or change their secretions and generate more free radicals. It appears that asbestos can suppress the immune system, and more research is needed to fully understand why and how. At any rate, eventually a tumor forms and begins to grow.

Diagnostic Steps

Mesothelioma diagnosis begins with a review of the medical history and if it reveals any history of asbestos exposure, the doctor’s antennae will go up. A physical exam follows, and a chest X-ray.

· There may be lung function tests to assess the volume of air that the lungs can hold and the speed at which they can inhale and exhale.

· Asbestos exposure typically creates a thickening in the lung tissue, so if the X-ray reveals this, a CT scan or MRI will be performed.

· If fluid has accumulated in the lungs, some will be aspirated with a syringe and tested for abnormal cells. At this point, the doctor may diagnose tuberculosis or heart failure.

· To confirm the presence of mesothelioma, a biopsy will be done. The doctor will take a sample of tissue and send it to a pathologist to examine under a microscope.

It is not fully understood at the molecular level how mesothelioma begins. It is still a fairly rare form of cancer, although incidence rates have risen during the past 20 years. In Western countries, it appears between seven and forty times per million people.

Most people who are being diagnosed with mesothelioma were exposed to asbestos on the job. Adequate protection was not provided by the employer, such as breathing masks or special clothing worn only on the job. Workers who came home wearing the same clothing as they had worked in brought asbestos fibers home with them. That meant that whoever did their laundry could well have been exposed to the asbestos also.