| Asbestos Diseases
Mesothelioma
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. Virtually all cases
of malignant mesothelioma are attributable to asbestos exposure.
Frequently Asked
Questions (click on a link)
What is mesothelioma?
What are the key statistics about
mesothelioma?
What are the different types of
mesothelioma?
What are the risk factors for
mesothelioma?
What causes
mesothelioma?
What are the signs and symptoms of
mesothelioma?
How is mesothelioma
diagnosed?
How is mesothelioma
staged?
What treatments are available for
mesothelioma?
Lung Cancer
Lung cancer occurs when malignant cells originate in the lung. It is the
most common asbestos-related cancer found in present or ex-smokers who have
a history of asbestos exposure.
Asbestosis
Asbestosis is the scarring of the tissue of the lung itself from inhalation
of airborne asbestos fibers. Many doctors who do not have a good understanding
of asbestos-related diseases tend to use the term "asbestosis" as a buzzword
for any and all conditions related to asbestos.
Pleural Disease
Pleural disease is any scarring of the pleura -- the lining of the lung.
It is evidence that an individual has sustained a heavy enough response to
asbestos to be at substantial risk for more serious disease.
Medical History of Asbestos Diseases
Here we have compiled a summary of the History of Asbestos Disease as reported
in the world medical literature. This list of events reflects findings of
a medical nature. A similar timeline of significant dates in the legal pursuit
of asbestos-related compensation is available in the Asbestos Industry section
of our site.
Mesothelioma
What is mesothelioma?
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.
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.
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 than the relationship between mesothelioma
and asbestos exposure has been confirmed in studies around the world.
The incidence of mesothelioma in the United States
remains very low, with 14 cases occurring per million people per year. Despite
these numbers the noticed threefold increase in mesothelioma in males between
1970 and 1984, is directly associated with environmental and occupational
exposure to asbestos, mostly in areas of asbestos product plants and shipbuilding
facilities.
Although the disease is much more commonly seen in
60-year old men, it has been described in women and early childhood as well.
The cause of the disease is not so well understood in these latter two groups,
but there is some evidence of possible asbestos exposure for some of these
cases as well.
Malignant mesotheliomas are divided into three main
types. About 50% to 70% of mesotheliomas are the epithelioid type. This type
has the best prognosis (outlook for survival). The other two types are the
sarcomatoid type (7%-20%), and the mixed/biphasic type (20%-35%). Treatment
options for all three types are the same.
About three-fourths of mesotheliomas start in the chest
cavity. They are known as pleural mesotheliomas. Another 10% to 20% begin
in the abdomen. These are called peritoneal mesotheliomas. Pericardial
mesotheliomas, those starting in the cavity around the heart, are very rare.
The covering layer of the testicles is actually an outpouching of peritoneum
into the scrotum. Mesotheliomas that affect this covering of the testicles
are quite rare.
What are the key statistics
about mesothelioma?
Mesothelioma is fairly rare. There are an estimated
2,000 to 3,000 new cases per year of mesothelioma in the United States, but
this figure appears to be increasing.
The average age at diagnosis is 50 to 70 years old.
The disease affects men 3 to 5 times more often than women. Mesothelioma
is less common in African Americans than in white Americans.
Mesothelioma is a serious disease. By the time the
symptoms appear and cancer is diagnosed, the disease is often advanced. The
average survival time is about one year. However, if the cancer is found
early and treated aggressively, almost half of the patients whose cancer
is found early reach the two-year mark, and about 20% survive five
years.
The 5-year survival rate refers to the percent of patients
who live at least 5 years after their cancer is diagnosed. Many of these
patients live much longer than 5 years after diagnosis, and 5-year rates
are used to produce a standard way of discussing prognosis. Five-year relative
survival rates exclude from the calculations patients dying of other diseases,
and are considered to be a more accurate way to describe the prognosis for
patients with a particular type and stage of cancer. Of course, 5-year survival
rates are based on patients diagnosed and initially treated more than 5 years
ago. Improvements in treatment often result in a more favorable outlook for
recently diagnosed patients.
What are the different
types of mesothelioma?
Pleural Mesothelioma
Pleural mesothelioma spreads within the chest cavity, sometimes involving
the lung. Metastases can occur in any organ, including the brain, and are
much more common than previously thought.
The onset of mesothelioma is usually very slow, the
most common presenting symptom is persistent pain localized in the chest.
Sometimes the pain is accompanied by severe difficulty breathing, due to
an accumulation of fluid in the pleural space known as pleural effusion.
Cough, weight loss and fever are not uncommon. The most valuable single test
to show the extent of the disease is a computed chest tomograph (CT-scan).
There are currently no serum markers available for
the diagnosis of mesothelioma. The detection of elevated serum levels of
hyaluronic acid may be useful in differentiating mesotheliomas from other
tumors, or to follow the effect of treatment.
The median survival is about 17 months from the beginning
of symptoms. The 3-year survival is 10% the 5-year survival is approximately
5% ( if 100 patients are diagnosed with mesothelioma at a specific point
in time, that means that 10 patients will still be alive at the end of 3
years and 5 patients will only be alive at the end of 5 years).
Peritoneal Mesothelioma
Peritoneal mesothelioma involves the abdominal cavity, infiltrating the liver,
spleen or the bowel. As with pleural mesothelioma pain is the most common
presenting complaint. In addition, due to fluid accumulation in the abdominal
cavity (ascites), the abdomen appears enlarged. The patients experience nausea,
vomiting, swelling of their feet, fever and difficulty in moving their bowels.
The prognosis is poorer than for pleural mesothelioma
with a median survival time of about 10 months from the onset of
symptoms.
Benign Mesothelioma:
A rare form of mesothelioma is the cycstic mesothelioma of the peritoneum.
Its prognosis is benign. Its occurrence has been described primarily in young
women. However the diagnosis presents difficulties, requiring extensive electron
miscroscopy and immunohistochemical studies.
Rare Sites:
Mesothelioma of the pericardium, is a very seldom seen cardiac cancer. The
mass is usually detected at a late stage by echocardiography, the prognosis
is very poor , with or without therapy. Mesothelioma of the ovaries and the
scrotum have also been reported in the literature. The management differs
based on the stage of the disease, the prognosis is also very poor. The etiology
of the few cases of mesothelioma described in children remains unclear and
is not believed to be asbestos-related, the therapy and prognosis differ
on an individual basis.
What are the risk factors
for malignant mesothelioma?
A risk factor is anything that increases a person's chance of getting a disease
such as cancer. Different cancers have different risk factors. For example,
unprotected exposure to strong sunlight is a risk factor for skin cancer
and smoking is a risk factor for lung cancer as well as other types of cancer.
Scientists have found several risk factors that make a person more likely
to develop mesothelioma.
Asbestos:
The main risk factor for developing mesothelioma is exposure to
asbestos. Asbestos refers to a family of magnesium-silicate mineral fibers.
In the past, asbestos was used widely for insulation because it does not
conduct heat well and it is resistant to melting or burning. As the link
between asbestos and mesothelioma has become well known, the use of this
material has decreased. However, up to 8 million Americans may already have
been exposed to asbestos.
According to the United States Environmental Protection
Agency, as many as 733,000 schools and public buildings in the country today
contain asbestos insulation. As many as 10% to 15% of schools in the United
States may contain asbestos insulation. People who may be at risk for
occupational asbestos exposure include some miners, factory workers, insulation
manufacturers, railroad workers, ship builders, gas mask manufacturers, and
construction workers, particularly those involved with installing insulation.
Several studies have shown that family members of people exposed to asbestos
at work have an increased risk of developing mesothelioma, because asbestos
fibers are carried home on the clothes of the workers.
There are two main forms of asbestos -- serpentine
and amphiboles. Serpentine fibers are curly and pliable. Chrysotile is the
only type of serpentine fiber and it is the most widely used form of asbestos.
Amphiboles are thin, rod-like fibers of which there are 5 main types-crocidolite,
amosite, anthrophylite, tremolite, and actinolyte. Amphiboles (particularly
crocidolite) are considered to be the most carcinogenic (cancer-causing).
However, even the more commonly used chrysotile fibers have been associated
with malignant (cancerous) mesotheliomas and should be considered dangerous
as well.
It may be that asbestos causes cancer by physically
irritating cells rather than by a chemical effect. When fibers are inhaled,
most are cleared in the nose, throat, trachea (windpipe), or bronchi (large
breathing tubes of the lungs). Fibers are cleared by sticking to mucus inside
the air passages and being coughed up or swallowed. The long, thin, fibers
are less readily cleared, and they may reach the ends of the small airways
and penetrate into the pleural lining of the lung and chest wall. These fibers
may then directly injure mesothelial cells of the pleura, and eventually
cause mesothelioma.
Asbestos fibers can also damage cells of the lung and
result in asbestosis (formation of scar tissue in the lung), and/or lung
cancer. The risk of lung cancer among people exposed to asbestos is increased
by 7 times, compared with the general population. Indeed, asbestosis,
mesothelioma, and lung cancer are the three most frequent causes of death
and disease among people with heavy asbestos exposure. Peritoneal mesothelioma,
which forms in the abdomen, may result from coughing up and swallowing inhaled
asbestos fibers. Cancers of the larynx, pancreas, esophagus, colon, and kidney
have also been linked to asbestos exposure, but the increased risk is not
as great as with lung cancer.
The risk of developing a mesothelioma is related to
how much asbestos a person was exposed to and how long this exposure lasted.
People exposed at an early age, for a long period of time, and at higher
levels are most likely to develop this cancer. Mesotheliomas take a long
time to develop. The time between exposure to asbestos and diagnosis of
mesothelioma is usually between 20 and 40 years.
Although the risk of developing mesothelioma rises
with the amount of asbestos exposure, it is clear that genetic factors also
play a role in determining who develops the disease. This explains why not
all persons exposed to high levels of asbestos dust develop
mesothelioma.
Radiation: There have been a few published reports
of pleural and peritoneal mesotheliomas that developed following exposure
to thorium dioxide (Thorotrast). This material was used in the past by doctors
for certain x-ray tests. Because Thorotrast was found to cause cancers, it
has not been used for many years.
Zeolite: This is a silicate mineral, chemically related
to asbestos, common in the soil of the Anatoli region of Turkey. A few cases
of mesothelioma have been described in this region and may have been caused
by this mineral.
Simian Virus 40 (SV40): This virus has recently been
identified by researchers in human mesothelioma cells, and has been shown
to induce mesothelioma in the animal model. Polio vaccines administered as
a primary prevention measure during 1955 - 1961 have been shown to be
contaminated with SV40. However the implications of these facts are not totally
understood and further research will be needed to clarify the link between
malignant mesothelioma and a viral etiology.
Tobacco: Although tobacco smoking has not been associated
with the development of mesotheliomas, the combination of smoking and asbestos
exposure greatly increases the risk of lung cancer. Asbestos workers who
also smoke have a lung cancer risk 50 to 90 times greater than that of the
general population. More asbestos workers die of lung cancer than of
mesothelioma.
What causes
mesothelioma?
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 are the signs
and symptoms of mesothelioma?
Early symptoms of mesotheliomas are not specific to the disease. People often
ignore them or mistake them for common, minor ailments. Most people with
mesothelioma have symptoms for only 2 to 3 months before they are diagnosed.
About one-fourth have symptoms for at least six months prior to their
diagnosis.
Over half of patients with pleural mesothelioma have
pain in the lower back or at the side of the chest. Many report shortness
of breath. A smaller percentage have trouble swallowing, cough, fever, sweating,
fatigue, and weight loss. Other symptoms include hoarseness, coughing up
blood, swelling of the face and arms, muscle weakness, and sensory loss.
Symptoms of peritoneal mesothelioma include abdominal
(belly) pain, weight loss, nausea, and vomiting. There may also be a hernia,
fluid in the abdominal cavity or a mass in the abdomen.
A person with any of these symptoms who has been exposed
to asbestos should see a doctor right away.
How is mesothelioma
diagnosed?
If there is a reason to suspect you may have a mesothelioma, the doctor will
use one or more methods to find out if the disease is really present.
Medical history and physical
examination:
A complete medical history (interview) is taken to check for risk factors
and symptoms. This will include questions to determine if you have been exposed
to asbestos.
A physical exam will provide information about signs
of mesothelioma and other health problems. Patients with pleural mesotheliomas
(mesotheliomas of the chest) often have pleural effusion (fluid in their
chest cavity) caused by the cancer. Ascites (fluid in the abdominal cavity)
in cases of peritoneal mesothelioma, and pericardial effusion (fluid in the
pericardium) in cases of pericardial mesothelioma can also be detected during
a physical exam.
Imaging tests:
A chest x-ray may show irregular thickening of the pleura, pleural calcifications
(mineral deposits), lowering of the lung fissures (spaces between the lobes
of the lungs), and fluid in the pleural space. These findings suggest asbestos
exposure leading to the development of a mesothelioma.
Imaging studies such as x-rays, computed tomography
(CT) scans, and magnetic resonance imaging (MRI) scans will help determine
the location, size, and extent of the cancer. The CT scan uses a rotating
x-ray beam to create a series of pictures of the body from many angles. A
computer combines these pictures to produce detailed cross-sectional images
of a selected part of the body. To highlight details on the CT scan, you
may be asked for permission to have a harmless dye injected into a vein.
MRI uses magnetic fields instead of x-rays to create images of selected areas
of the body. As with the CT scan, a computer generates a detailed cross-sectional
image.
Tests of fluid and tissue
samples:
In patients with a pleural effusion, a sample of this fluid can be removed
by inserting a needle into the chest cavity. A similar technique can be used
to obtain abdominal fluid and pericardial fluid. The fluid is then tested
to show its chemical make up and viewed under a microscope to determine whether
cancer cells are present.
A tissue sample of a pleural or pericardial tumor can
be obtained using a relatively new technique called thoracoscopy. A thoracoscope
(telescope-like instrument connected to a video camera) is inserted through
a small incision into the chest. The doctor can see the tumor through the
thoracoscope, and can use special forceps to take a tissue biopsy. Similarly,
laparoscopy can be used to see and obtain a biopsy of a peritoneal tumor.
In this procedure, a flexible tube attached to a video camera is inserted
into the abdominal cavity through small incisions on the front of the abdomen.
Fluid can also be collected during thoracoscopy or laparoscopy.
Surgery, either a thoracotomy (which opens the chest
cavity) or a laparotomy (which opens the abdominal cavity), allows the surgeon
to remove a larger sample of tumor or, sometimes, to remove the entire
tumor.
For patients who might have pleural mesothelioma, the
doctor may also do a bronchoscopy. In this procedure a flexible lighted tube
is inserted through the mouth, down the trachea, and into the bronchi to
see if there are other masses in the airway. Small samples of abnormal-appearing
tissue can be removed for testing.
The patient may also have a mediastinoscopy. A lighted
tube is inserted under the sternum (chest bone) at the level of the neck
and moved down into the chest. Mediastinoscopy allows the surgeon to view
the lymph nodes in this area and remove samples to check for cancer. Lymph
nodes are bean-sized collections of immune system cells that help the body
fight infections and cancers. Cancers arising in the lung often spread to
lymph nodes, but mesotheliomas rarely do this. Tests of lymph nodes can give
the doctor information on whether a cancer is still localized or if it has
started to spread, and can help distinguish lung cancer from
mesothelioma.
It is often hard to diagnose mesothelioma by looking
at the cells from the fluid around the lungs, abdomen or heart. It is even
hard to diagnose mesothelioma with tissue from biopsies. Under the microscope,
mesothelioma can look like several other types of cancer. For example, pleural
mesothelioma may resemble some types of lung cancer and peritoneal mesothelioma
may resemble some cancers of the ovaries. For this reason, special laboratory
tests are often done to help distinguish mesothelioma from some other cancers.
These tests often use special techniques to recognize certain markers (types
of chemicals) known to be contained in mesotheliomas. Different markers are
present in cancer of the lung or ovary. The electron microscope can sometimes
be helpful in diagnosing mesothelioma. This microscope can magnify samples
more than 100 times greater than the light microscope which is generally
used in cancer diagnosis. This stronger microscope makes it possible to see
small parts of the cancer cells that distinguish mesothelioma from other
types of cancer.
The diagnosis of mesothelioma presents problems primarily
initially in the distinction between mesothelioma and other forms of cancer
such as adenocarcinoma or benign, noncancerous pleural inflammation. The
best diagnostic tools at the moment remain the open pleural biopsy performed
during thoracoscopy. This procedure also allows for direct visualization
of the inside of the chest, and information of involvment of other organs
and extension of disease. Other procedures with lower yields are CT guided
pleural biopsy, or blind pleural biopsy. In addition to the gross appearance
of the tumor, pathologists often rely on a panel of histochemical and
immunohistochemical stains to diagnose or exclude meosothelioma. Currently
markers linked to prognosis of mesothelioma are under study, but have not
been validated for the general use.
How is mesothelioma
staged?
Staging is the process of finding out how far the cancer has spread. Staging
of mesothelioma is based on imaging studies such as x-rays, CT scans, and
MRI scans. The treatment and outlook for patients with mesothelioma largely
depends on the stage (extent of spread) of their cancer. Since pleural
mesothelioma occurs most frequently and has been studied the most, it is
the only mesothelioma for which a staging classification exists.
The staging system most often used for mesothelioma
is the Butchart system. This system is based mainly on the extent of the
primary tumor mass, and divides mesotheliomas into stages I through IV.
Butchart Staging System
Stage I: Mesothelioma is present within the right or left pleura, and may
also involve the lung, pericardium, or diaphragm (the muscle separating the
chest from the abdomen) on the same side.
Stage II: Mesothelioma invades the chest wall or involves
the esophagus (food passage connecting the throat to the stomach), heart,
or pleura on both sides. The lymph nodes in the chest may also be
involved.
Stage III: Mesothelioma has penetrated through the
diaphragm into the peritoneum (lining of the abdominal cavity). Lymph nodes
beyond those in the chest may also be involved.
Stage IV: There is evidence of distant metastases (spread
through the bloodstream to other organs).
Another staging system has recently been developed
by the American Joint Committee on Cancer (AJCC). This is a TNM system, similar
to staging systems used for most other cancers. T stands for tumor (its size
and how far it has spread to nearby organs), N stands for spread to lymph
nodes and M is for metastasis (spread to distant organs). In TNM staging,
information about the tumor, lymph nodes, and metastasis is combined in a
process called stage grouping to assign a stage described by Roman numerals
from I to IV. Minor differences exist between the AJCC TNM staging system
and the Butchart staging system.
TNM Staging System
Stage I: Mesothelioma involves the right or left pleura. It may also have
spread into the lung, pericardium, or diaphragm on the same side. It has
not yet spread to the lymph nodes.
Stage II: Mesothelioma has spread from the pleura on
one side to the nearby peribronchial and/or hilar lymph nodes next to the
lung on the same side. It may also have spread into the lung, pericardium,
or diaphragm on the same side.
Stage III: Mesothelioma has spread into the chest wall
muscle, ribs, heart, esophagus, or other organs in the chest on the same
side as the primary tumor, with or without spread to subcarinal and/or
mediastinal lymph nodes on the same side as the main tumor. Subcarinal nodes
are located at the point where the windpipe branches to the left and right
lungs. Mediastinal lymph nodes are located in the space behind the chest
bone in front of the heart. Mesotheliomas with the same extent of local spread
as in stage II that have also spread to subcarinal and/or mediastinal lymph
nodes on the same side are also included in stage III.
Stage IV: Mesothelioma has spread into the lymph nodes
in the chest on the side opposite that of the primary tumor, or directly
extends to the pleura or lung on the opposite side, or directly extends into
the peritoneum, or directly extends into organs in the abdominal cavity or
neck. Any mesothelioma with evidence of distant metastases (spread to other
organs through the bloodstream) or spread to organs beyond the chest or abdomen
is included in this stage.
Although the recently developed TNM classification
is the most detailed and precise, the original Butchart staging system is
still used most often to describe the spread of pleural mesotheliomas.
Understanding these staging systems for mesothelioma is important both for
estimating and better understanding prognosis, and also for assessing therapeutic
options.
Prognostic Factors:
Because pleural mesothelioma has been better studied than peritoneal mesothelioma
we know more about factors associated with prognosis for pleural mesothelioma.
Younger age at diagnosis, performance status (functional status) and absence
of weight loss are associated with a more favorable prognosis.
Mesotheliomas are usually of three different cell types
(histological analysis): 1) epithelial cell type - has the most favorable
prognosis; 2) fibrosarcomatous cell type - carries the worst prognosis and
3) mixed cell type - has an intermediate prognosis.
What treatments are
available for Mesothelioma?
Conventional Treatments
Experimental Treatments
Clinical Trials
Mesothelioma Treatment by Stage
Questions to ask your Doctor
Leading Cancer Centers
Leading Mesothelioma Physicians
Articles and Abstracts
Other Sources for Information
Disclaimer
Please note that articles on this 'Perfect Options' site do not constitute
professional advice, which recommends a course of action based upon the specifics
of your personal circumstances. The articles are intended to provide general
view of asbestos related cancer. We urge you to consult a solicitor before
making any important decisions.
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