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Date reviewed: 04/18/2001
Editorial changes made: 05/13/2002
Mesothelioma is a rare form of cancer in
which malignant (cancerous) cells are found in the
mesothelium, a protective sac that covers most of the body's
internal organs. Most people who develop mesothelioma have
worked on jobs where they inhaled asbestos particles.
1. What is
the mesothelium?
The mesothelium is a membrane that covers and protects most
of the internal organs of the body. It is composed of two
layers of cells: One layer immediately surrounds the organ;
the other forms a sac around it. The mesothelium produces a
lubricating fluid that is released between these layers,
allowing moving organs (such as the beating heart and the
expanding and contracting lungs) to glide easily against
adjacent structures.
The mesothelium
has different names, depending on its location in the body.
The peritoneum is the mesothelial tissue that covers most of
the organs in the abdominal cavity. The pleura is the
membrane that surrounds the lungs and lines the wall of the
chest cavity. The pericardium covers and protects the heart.
The mesothelial tissue surrounding the male internal
reproductive organs is called the tunica vaginalis testis.
The tunica serosa uteri covers the internal reproductive
organs in women.
2. What is
mesothelioma?
Mesothelioma (cancer of the mesothelium) is a disease in
which cells of the mesothelium become abnormal and divide
without control or order. They can invade and damage nearby
tissues and organs. Cancer cells can also metastasize
(spread) from their original site to other parts of the
body. Most cases of mesothelioma begin in the pleura or
peritoneum.
3. How common
is mesothelioma?
Top
Although reported
incidence rates have increased in the past 20 years,
mesothelioma is still a relatively rare cancer. About 2,000
new cases of mesothelioma are diagnosed in the United States
each year. Mesothelioma occurs more often in men than in
women and risk increases with age, but this disease can
appear in either men or women at any age.
4. What are
the risk factors for mesothelioma?
Working with
asbestos is the major risk factor for mesothelioma. A
history of asbestos exposure at work is reported in about 70
percent to 80 percent of all cases. However, mesothelioma
has been reported in some individuals without any known
exposure to asbestos.
Asbestos is the name of a group of minerals that occur
naturally as masses of strong, flexible fibers that can be
separated into thin threads and woven. Asbestos has been
widely used in many industrial products, including cement,
brake linings, roof shingles, flooring products, textiles,
and insulation. If tiny asbestos particles float in the air,
especially during the manufacturing process, they may be
inhaled or swallowed, and can cause serious health problems.
In addition to mesothelioma, exposure to asbestos increases
the risk of lung cancer, asbestosis (a noncancerous, chronic
lung ailment), and other cancers, such as those of the
larynx and kidney.
Smoking does not appear to increase the risk of mesothelioma.
However, the combination of smoking and asbestos exposure
significantly increases a person's risk of developing cancer
of the air passageways in the lung.
5. Who is at
increased risk for developing mesothelioma?
Top
Asbestos has been
mined and used commercially since the late 1800s. Its use
greatly increased during World War II. Since the early
1940s, millions of American workers have been exposed to
asbestos dust. Initially, the risks associated with asbestos
exposure were not known. However, an increased risk of
developing mesothelioma was later found among shipyard
workers, people who work in asbestos mines and mills,
producers of asbestos products, workers in the heating and
construction industries, and other tradespeople. Today, the
U.S. Occupational Safety and Health Administration (OSHA)
sets limits for acceptable levels of asbestos exposure in
the workplace. People who work with asbestos wear personal
protective equipment to lower their risk of exposure.
The risk of asbestos-related disease increases with heavier
exposure to asbestos and longer exposure time. However, some
individuals with only brief exposures have developed
mesothelioma. On the other hand, not all workers who are
heavily exposed develop asbestos-related diseases.
There is some evidence that family members and others living
with asbestos workers have an increased risk of developing
mesothelioma, and possibly other asbestos-related diseases.
This risk may be the result of exposure to asbestos dust
brought home on the clothing and hair of asbestos workers.
To reduce the chance of exposing family members to asbestos
fibers, asbestos workers are usually required to shower and
change their clothing before leaving the workplace.
6. What are
the symptoms of mesothelioma?
Symptoms of
mesothelioma may not appear until 30 to 50 years after
exposure to asbestos. Shortness of breath and pain in the
chest due to an accumulation of fluid in the pleura are
often symptoms of pleural mesothelioma. Symptoms of
peritoneal mesothelioma include weight loss and abdominal
pain and swelling due to a buildup of fluid in the abdomen.
Other symptoms of peritoneal mesothelioma may include bowel
obstruction, blood clotting abnormalities, anemia, and
fever. If the cancer has spread beyond the mesothelium to
other parts of the body, symptoms may include pain, trouble
swallowing, or swelling of the neck or face.
These symptoms may be caused by mesothelioma or by other,
less serious conditions. It is important to see a doctor
about any of these symptoms. Only a doctor can make a
diagnosis.
7. How is
mesothelioma diagnosed?
Top
Diagnosing
mesothelioma is often difficult, because the symptoms are
similar to those of a number of other conditions. Diagnosis
begins with a review of the patient's medical history,
including any history of asbestos exposure. A complete
physical examination may be performed, including x-rays of
the chest or abdomen and lung function tests. A CT (or CAT)
scan or an MRI may also be useful. A CT scan is a series of
detailed pictures of areas inside the body created by a
computer linked to an x-ray machine. In an MRI, a powerful
magnet linked to a computer is used to make detailed
pictures of areas inside the body. These pictures are viewed
on a monitor and can also be printed.
A biopsy is needed to confirm a diagnosis of mesothelioma.
In a biopsy, a surgeon or a medical oncologist (a doctor who
specializes in diagnosing and treating cancer) removes a
sample of tissue for examination under a microscope by a
pathologist. A biopsy may be done in different ways,
depending on where the abnormal area is located. If the
cancer is in the chest, the doctor may perform a
thoracoscopy. In this procedure, the doctor makes a small
cut through the chest wall and puts a thin, lighted tube
called a thoracoscope into the chest between two ribs.
Thoracoscopy allows the doctor to look inside the chest and
obtain tissue samples. If the cancer is in the abdomen, the
doctor may perform a peritoneoscopy. To obtain tissue for
examination, the doctor makes a small opening in the abdomen
and inserts a special instrument called a peritoneoscope
into the abdominal cavity. If these procedures do not yield
enough tissue, more extensive diagnostic surgery may be
necessary.
If the diagnosis is mesothelioma, the doctor will want to
learn the stage (or extent) of the disease. Staging involves
more tests in a careful attempt to find out whether the
cancer has spread and, if so, to which parts of the body.
Knowing the stage of the disease helps the doctor plan
treatment.
Mesothelioma is described as localized if the cancer is
found only on the membrane surface where it originated. It
is classified as advanced if it has spread beyond the
original membrane surface to other parts of the body, such
as the lymph nodes, lungs, chest wall, or abdominal organs.
8. How is
mesothelioma treated?
Treatment for
mesothelioma depends on the location of the cancer, the
stage of the disease, and the patient's age and general
health. Standard treatment options include surgery,
radiation therapy, and chemotherapy. Sometimes, these
treatments are combined
- Surgery is a common treatment for
mesothelioma. The doctor may remove part of the lining of
the chest or abdomen and some of the tissue around it. For
cancer of the pleura (pleural mesothelioma), a lung may be
removed in an operation called a pneumonectomy. Sometimes
part of the diaphragm, the muscle below the lungs that
helps with breathing, is also removed.
- Radiation therapy, also called
radiotherapy, involves the use of high-energy rays to kill
cancer cells and shrink tumors. Radiation therapy affects
the cancer cells only in the treated area. The radiation
may come from a machine (external radiation) or from
putting materials that produce radiation through thin
plastic tubes into the area where the cancer cells are
found (internal radiation therapy).
- Chemotherapy is the use of anticancer
drugs to kill cancer cells throughout the body. Most drugs
used to treat mesothelioma are given by injection into a
vein (intravenous, or IV). Doctors are also studying the
effectiveness of putting chemotherapy directly into the
chest or abdomen (intracavitary chemotherapy).
To relieve
symptoms and control pain, the doctor may use a needle or a
thin tube to drain fluid that has built up in the chest or
abdomen. The procedure for removing fluid from the chest is
called thoracentesis. Removal of fluid from the abdomen is
called paracentesis. Drugs may be given through a tube in
the chest to prevent more fluid from accumulating. Radiation
therapy and surgery may also be helpful in relieving
symptoms.
9. Are new
treatments for mesothelioma being studied?
Top
Yes. Because
mesothelioma is very hard to control, the National Cancer
Institute (NCI) is sponsoring clinical trials (research
studies with people) that are designed to find new
treatments and better ways to use current treatments. Before
any new treatment can be recommended for general use,
doctors conduct clinical trials to find out whether the
treatment is safe for patients and effective against the
disease. Participation in clinical trials is an important
treatment option for many patients with mesothelioma.
People interested in taking part in a clinical trial should
talk with their doctor. Information about clinical trials is
available from the Cancer Information Service (CIS) (see
below) at 18004CANCER. Information specialists at the CIS
use PDQ®, NCI's cancer information database, to identify and
provide detailed information about specific ongoing clinical
trials. Patients also have the option of searching for
clinical trials on their own. The clinical trials page on
the NCI's Cancer.gov Web site, located at http://cancer.gov/clinical_trials
on the Internet, provides general information about clinical
trials and links to PDQ.
People considering clinical trials may be interested in the
NCI booklet Taking Part in Clinical Trials: What Cancer
Patients Need To Know. This booklet describes how research
studies are carried out and explains their possible benefits
and risks. The booklet is available by calling the CIS, or
from the NCI Publications Locator Web site at http://cancer.gov/publications
on the Internet.
Sources
of National Cancer Institute Information
Cancer Information Service
Toll-free: 18004CANCER (18004226237)
TTY (for deaf and hard of hearing callers): 18003328615
NCI Online
Internet
Use
http://cancer.gov
to reach NCI's Web site
LiveHelp
Top
Cancer
Information Specialists offer online assistance through the
LiveHelp
link on the NCI's Web site.
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