Asbestos exposure is the main cause of mesothelioma. After these fibers
are breathed in, they travel to the ends of small air passages and reach
the pleura where they cause physical damage to mesothelial cells that may
result in cancer. In addition, they also cause injury to lung cells that
can result in lung cancer and/or asbestosis (replacement of lung tissue by
scar tissue). If swallowed, these fibers can reach the abdominal cavity
where they have a role in causing peritoneal mesothelioma.
Exposure to asbestos, though mostly occupational, can
also be environmental, or familial by household contamination, through the
work clothes of an asbestos worker for instance.
Beginning 15 years after the onset of exposure, about
6% of asbestos workers die of mesothelioma. In one study of asbestos
insulation workers, the death rate from mesothelioma was 344 times higher
than in the general population. (Selifoff IJ et al. Relation between
exposure to asbestos and mesothelioma. NEJM)
What is
mesothelioma?
Mesothelioma is cancer of
the mesothelium – the membrane that lines the interior of the chest and
abdomen and surrounds the internal organs. Mesothelioma is very rare: the
only known cause is asbestos exposure. It occurs when asbestos fibers –
particularly those of crocidolite asbestos, which are thin and straight –
penetrate the mesothelial tissue and cause inflammation; this causes a
tumor to form.
Most cases of mesothelioma infect the pleura, which is the mesothelial
layer that surrounds the lungs and lines the chest cavity. Pleural
mesothelioma usually occurs from asbestos inhalation.
Mesothelioma can also occur in the peritoneum – the mesothelium of the
abdominal cavity – or the pericardium – the mesothelial lining around the
heart. Peritoneal or pericardial mesothelioma may occur as a result of
either pleural mesothelioma that has migrated or from ingestion of
asbestos.
Malignant mesothelioma, a rare form of cancer, is a disease in which
cancer (malignant) cells are found in the sac lining the chest (the
pleura) or abdomen (the peritoneum). Most people with malignant
mesothelioma have worked on jobs where they breathed asbestos.
A doctor should be seen if a person has shortness of breath, pain in
the chest, or pain or swelling in the abdomen. If there are symptoms, the
doctor may order an x-ray of the chest or abdomen.
The doctor may look inside the chest cavity with a special instrument
called a thoracoscope. A cut will be made through the chest wall and the
thoracoscope will be put into the chest between two ribs. This test,
called thoracoscopy, is usually done in the hospital. Before the test, the
patient will be given a local anesthetic (a drug that causes a loss of
feeling for a short period of time). Some pressure may be felt, but
usually there is no pain.
The doctor may also look inside the abdomen (peritoneoscopy) with a
special tool called a peritoneoscope. The peritoneoscope is put into an
opening made in the abdomen. This test is also usually done in the
hospital. Before the test is done, a local anesthetic will be given.
If tissue that is not normal is found, the doctor will need to cut out
a small piece and have it looked at under a microscope to see if there are
any cancer cells. This is called a biopsy. Biopsies are usually done
during the thoracoscopy or peritoneoscopy.
The chance of recovery (prognosis) depends on the size of the cancer,
where the cancer is, how far the cancer has spread, how the cancer cells
look under the microscope, how the cancer responds to treatment, and the
patient's age.
