Mesothelioma (cancer of the mesothelium) is a disease in which
cells of the mesothelium become abnormal and divide without control or
order. Mesothelioma is a cancer of the linings of the lungs, chest,
abdomen, and the organs contained in those areas, rather than a cancer
that forms in the lungs.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. Mesothelioma is most frequently caused by
exposure to asbestos. Asbestos is a group of naturally occurring minerals.
Asbestos releases strong, microscopic fibers that may injure the
protective linings surrounding the body's organs.Most cases of
mesothelioma begin in the pleura or peritoneum.
Malignant mesothelioma is an uncommon, but
no longer rare, cancer that is difficult to diagnose and poorly responsive
to therapy. Malignant mesothelioma is the most serious of all
asbestos-related diseases. Thousands of Americans die each year from
asbestos related disease including mesothelioma cancer.
A layer of
specialized cells called mesothelial cells lines the chest cavity,
abdominal cavity, and the cavity around the heart. These cells also cover
the outer surface of most internal organs. The tissue formed by these
cells is called mesothelium.There are three main types of malignant
mesothelioma: epithelial, sarcomatoid and mixed. The epithelial type is
the most common.
The mesothelium helps protect
the organs by producing a special lubricating fluid that allows organs to
move around. For example, this fluid makes it easier for the lungs to move
inside the chest during breathing. The mesothelium of the chest is called
the pleura and the mesothelium of the abdomen is known as the peritoneum.
The mesothelium of the pericardial cavity (the "sac-like" space around the
heart) is called the pericardium.
Tumors of the mesothelium can be
benign (noncancerous) or malignant (cancerous). A malignant tumor of the
mesothelium is called a malignant mesothelioma. Because most mesothelial
tumors are cancerous, malignant mesothelioma is often simply called
mesothelioma.
Mesothelioma was recognized as a
tumor of the pleura, peritoneum and pericardium in the late 1700's.
However it was not until much later, in 1960, that this particular type of
tumor was described in more detail and even more importantly, its
association with asbestos exposure was recognized. The first report
linking mesothelioma to asbestos exposure was written by J.C.Wagner, and
described 32 cases of workers in the "Asbestos Hills" in South Africa.
Since then, the relationship between mesothelioma and asbestos exposure
has been confirmed in studies around the world. Once it develops, this
type of cancer will continue to grow and spread until it is
treated.
About three-fourths of malignant mesothelioma occurrences
start in the chest cavity and is known as pleural mesothelioma. Another
10% to 20% begin in the abdomen and is called peritoneal mesothelioma.
Pericardial mesothelioma, starting in the cavity around the heart, is very
rare. The covering layer of the testicles is actually an out pouching of
peritoneum into the scrotum. Mesothelioma that affects this covering of
the testicles is quite rare.
About 90 percent of people who are
diagnosed with malignant mesothelioma have chest pain or shortness of
breath as the first symptoms of the disease. Chest pain is caused mainly
by the cancer itself, which irritates nerve cells in nearby tissues. Less
severe chest discomfort and shortness of breath generally are caused by a
collection of fluid between the two layers of the pleura in the chest, not
by the cancer itself. This collection of fluid is called a pleural
effusion. People with mesothelioma that develops in the abdominal lining
can have abdominal pain and swelling caused by an accumulation of fluid in
the abdominal cavity. Other possible symptoms include cough, fatigue and
unexplained weight loss.
Mesothelioma is not caused by smoking, as
lung cancer so often is. Instead, mesothelioma is tied almost exclusively
to the mineral asbestos. Of the 2,000 new cases of mesothelioma reported
in the United States each year, 70 to 80 percent can be traced to tiny,
airborne shards of asbestos, which in the past was used in the production
of construction materials ranging from cement to shingles to siding, and
was extensively used as insulation.
Mesothelioma also is not a
disease of the past. Although protections against occupational asbestos
exposure have been in place since the 1970s, asbestos-related cancers such
as mesothelioma can take 30 to 50 years to show up, according to the
Mesothelioma Applied Research Foundation.
There are several
misconceptions about mesothelioma. For one thing, it is not lung
cancer. It is a cancer of the two-layered membrane that covers and
protects most of the body’s organs. That membrane, the mesothelium, is
also called pericardium where it covers the heart, peritoneum where it
surrounds most of the other abdominal organs, and pleura where it envelops
the lungs, which is also where it most often turns cancerous.
The
mesothelium of the chest is called the pleura
The mesothelium of
the abdomen is known as the peritoneum.
The mesothelium of the
pericardial cavity ("sac-like" space around the heart) is called the
pericardium.
About 50
to 70 percent of its occurrences are the epithelioid type: This type has
the best forecast (outlook for survival).
Need to find more on Mesothelioma? Try
searching below:
NCI as the originator and the NCI Web site,
www.cancer.gov, as the source.
