Mesoteliom

Mesothelioma
Classification and external
resources
Left sided mesothelioma with
mediastinal node enlargement :
CT scan.
ICD-10 C45.
ICD-9 163
ICD-O: M9050/3-9055
OMIM 156240
DiseasesDB 8074
MedlinePlus 000115
eMedicine med/1457
MeSH D008654
Mesothelioma, more precisely
malignant mesothelioma, is a
rare form of cancer that develops
from the protective lining that
covers many of the body's
internal organs, the mesothelium.
It is usually caused by exposure
to asbestos.[1]
Its most common site is the
pleura (outer lining of the lungs
and internal chest wall), but it
may also occur in the peritoneum
(the lining of the abdominal
cavity), the pericardium (a sac
that surrounds the heart),[2] or
the tunica vaginalis (a sac that
surrounds the testis).
Most people who develop
mesothelioma have worked on
jobs where they inhaled asbestos
and glass particles, or they have
been exposed to asbestos dust
and fiber in other ways. It has
also been suggested that
washing the clothes of a family
member who worked with
asbestos or glass can put a
person at risk for developing
mesothelioma.[3] Unlike lung
cancer, there is no association
between mesothelioma and
smoking, but smoking greatly
increases the risk of other
asbestos-induced cancers.[4]
Those who have been exposed
to asbestos often utilize
attorneys to collect damages for
asbestos-related disease,
including mesothelioma.
Compensation via asbestos funds
or lawsuits is an important issue
in mesothelioma (see asbestos
and the law).
The symptoms of mesothelioma
include shortness of breath due
to pleural effusion (fluid between
the lung and the chest wall) or
chest wall pain, and general
symptoms such as weight loss.
The diagnosis may be suspected
with chest X-ray and CT scan, and
is confirmed with a biopsy
(tissue sample) and microscopic
examination. A thoracoscopy
(inserting a tube with a camera
into the chest) can be used to
take biopsies. It allows the
introduction of substances such
as talc to obliterate the pleural
space (called pleurodesis), which
prevents more fluid from
accumulating and pressing on
the lung. Despite treatment with
chemotherapy, radiation therapy
or sometimes surgery, the
disease carries a poor prognosis.
Research about screening tests
for the early detection of
mesothelioma is ongoing.
Signs and symptoms
Symptoms or signs of
mesothelioma may not appear
until 20 to 50 years (or more)
after exposure to asbestos.
Shortness of breath, cough, and
pain in the chest due to an
accumulation of fluid in the
pleural space ( pleural effusion)
are often symptoms of pleural
mesothelioma.
Symptoms of peritoneal
mesothelioma include weight
loss and cachexia, abdominal
swelling and pain due to ascites
(a buildup of fluid in the
abdominal cavity). 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.
Mesothelioma that affects the
pleura can cause these signs and
symptoms:
Chest wall pain
Pleural effusion, or fluid
surrounding the lung
Shortness of breath
Fatigue or anemia
Wheezing, hoarseness, or cough
Blood in the sputum (fluid)
coughed up (hemoptysis)
In severe cases, the person may
have many tumor masses. The
individual may develop a
pneumothorax, or collapse of the
lung. The disease may
metastasize, or spread, to other
parts of the body.
Tumors that affect the abdominal
cavity often do not cause
symptoms until they are at a late
stage. Symptoms include:
Abdominal pain
Ascites, or an abnormal buildup
of fluid in the abdomen
A mass in the abdomen
Problems with bowel function
Weight loss
In severe cases of the disease,
the following signs and
symptoms may be present:
Blood clots in the veins, which
may cause thrombophlebitis
Disseminated intravascular
coagulation , a disorder causing
severe bleeding in many body
organs
Jaundice, or yellowing of the eyes
and skin
Low blood sugar level
Pleural effusion
Pulmonary emboli, or blood clots
in the arteries of the lungs
Severe ascites
A mesothelioma does not usually
spread to the bone, brain, or
adrenal glands. Pleural tumors
are usually found only on one
side of the lungs.
Cause
Working with asbestos is the
major risk factor for
mesothelioma.[5] In the United
States, asbestos is the major
cause of malignant
mesothelioma and has been
considered "indisputably"[6]
associated with the development
of mesothelioma. Indeed, the
relationship between asbestos
and mesothelioma is so strong
that many consider
mesothelioma a “signal” or
“sentinel” tumor.[7][8][9][10] A
history of asbestos exposure
exists in most cases. However,
mesothelioma has been reported
in some individuals without any
known exposure to asbestos. In
rare cases, mesothelioma has
also been associated with
irradiation, intrapleural thorium
dioxide ( Thorotrast), and
inhalation of other fibrous
silicates, such as erionite. Some
studies suggest that simian virus
40 (SV40) may act as a cofactor
in the development of
mesothelioma.[11]
Asbestos was known in
antiquity, but it was not mined
and widely used commercially
until the late 19th century. 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 publicly 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
official position of the U.S.
Occupational Safety and Health
Administration (OSHA) and the
U.S. EPA is that protections and
"permissible exposure limits"
required by U.S. regulations,
while adequate to prevent most
asbestos-related non-malignant
disease, they are not adequate to
prevent or protect against
asbestos-related cancers such as
mesothelioma.[12] Likewise, the
British Government's Health and
Safety Executive (HSE) states
formally that any threshold for
mesothelioma must be at a very
low level and it is widely agreed
that if any such threshold does
exist at all, then it cannot
currently be quantified. For
practical purposes, therefore, HSE
assumes that no such "safe"
threshold exists. Others have
noted as well that there is no
evidence of a threshold level
below which there is no risk of
mesothelioma.[13] There
appears to be a linear, dose-
response relationship, with
increasing dose producing
increasing disease.[14]
Nevertheless, mesothelioma may
be related to brief, low level or
indirect exposures to asbestos.
[6] The dose necessary for effect
appears to be lower for
asbestos-induced mesothelioma
than for pulmonary asbestosis or
lung cancer.[6] Again, there is no
known safe level of exposure to
asbestos as it relates to
increased risk of mesothelioma.
The duration of exposure to
asbestos causing mesothelioma
can be short. For example, cases
of mesothelioma have been
documented with only 1 –3
months of exposure.[15][16]
People who work with asbestos
wear personal protective
equipment to lower their risk of
exposure.
Latency, the time from first
exposure to manifestation of
disease, is prolonged in the case
of mesothelioma. It is virtually
never less than fifteen years and
peaks at 30–40 years.[6] In a
review of occupationally related
mesothelioma cases, the median
latency was 32 years.[17] Based
upon the data from Peto et al, the
risk of mesothelioma appears to
increase to the third or fourth
power from first exposure.[14]
Environmental exposures
Incidence of mesothelioma had
been found to be higher in
populations living near naturally
occurring asbestos. For example,
in central Cappadocia, Turkey,
mesothelioma was causing 50%
of all deaths in three small
villages — Tuzköy, Karain and
Sarıhıdır. Initially, this was
attributed to erionite, a zeolite
mineral with similar properties to
asbestos, however, recently,
detailed epidemiological
investigation showed that
erionite causes mesothelioma
mostly in families with a genetic
predisposition.[18][19] The
documented presence of
asbestos fibers in water supplies
and food products has fostered
concerns about the possible
impact of long-term and, as yet,
unknown exposure of the
general population to these
fibers.
Occupational
Exposure to asbestos fibers has
been recognized as an
occupational health hazard since
the early 20th century. Numerous
epidemiological studies have
associated occupational
exposure to asbestos with the
development of pleural plaques,
diffuse pleural thickening,
asbestosis, carcinoma of the lung
and larynx, gastrointestinal
tumors, and diffuse malignant
mesothelioma of the pleura and
peritoneum. Asbestos has been
widely used in many industrial
products, including cement,
brake linings, gaskets, roof
shingles, flooring products,
textiles, and insulation.
Commercial asbestos mining at
Wittenoom, Western Australia,
occurred between 1945 and
1966. A cohort study of miners
employed at the mine reported
that while no deaths occurred
within the first 10 years after
crocidolite exposure, 85 deaths
attributable to mesothelioma had
occurred by 1985. By 1994, 539
reported deaths due to
mesothelioma had been reported
in Western Australia.
Paraoccupational secondary
exposure
Family members and others living
with asbestos workers have an
increased risk of developing
mesothelioma, and possibly
other asbestos related diseases.
[20][21] 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 fibres, asbestos
workers are usually required to
shower and change their
clothing before leaving the
workplace.
Asbestos in buildings
Many building materials used in
both public and domestic
premises prior to the banning of
asbestos may contain asbestos.
Those performing renovation
works or DIY activities may
expose themselves to asbestos
dust. In the UK use of Chrysotile
asbestos was banned at the end
of 1999. Brown and blue
asbestos was banned in the UK
around 1985. Buildings built or
renovated prior to these dates
may contain asbestos materials