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What is Mesothelioma? Mesothelioma from
the (Greek meso+ thelioma, tumor of middle lining tissue) is an
uncommon cancer, originating from the cells which form the membrane
lining the abdominal cavity (peritoneal membrane or peritoneum)
which houses the intestines, or the chest (pleural membrane or
pleura) cavity housing the heart and lungs, in which the cells
making up those tissues begin to grow out of control.
Mesotheliomas most often are seen in older patients, more often
men that have a history of occupational exposure to asbestos,
although other causes such as radiation and certain viruses have
occasionally been implicated. In a proportion of cases, no asbestos
exposure can be identified.
Mesotheliomas involving the lung and pleura characteristically
present as progressive shortness of breath due to the thickening
of the lining membrane of the lung with gradual contraction of
the breathing space; often, fluid accumulates in the lung spaces
as well, further interfering with breathing, Mesotheliomas involving
the abdominal cavity present with digestive symptoms, and abdominal
swelling due to thickening of the lining membranes of the gut,
and accumulation of large amounts of fluid in the abdomen.
How serious is it ? Mesotheliomas are serious and potentially
life-threatening. Survival of patients with mesothelioma is usually
short if effective treatment is not found, especially those with
tumors that can be shown to be growing aggressively. Because mesotheliomas
have usually spread throughout the pleural or peritoneal cavity
before the diagnosis is made, complete surgical removal is only
rarely possible. Moreover, mesotheliomas are not as sensitive
to radiation therapy or chemotherapy as are many other tumors.
How are mesotheliomas diagnosed? In all cases, the diagnosis
of mesothelioma must first be unquestionably established by biopsy
of affected or suspicious tissues, and by definitive microscopic
examination by a trained pathologist. Biopsy almost always requires
an invasive procedure such as thoracoscopy and pleural biopsy,
or laparotomy or laparoscopy, The removed tissues may be treated
with special biological or chemical stains which are used to help
the pathologist establish a firm diagnosis. The pathologist usually
also comments upon the rate of growth and biological virulence
of the tumor
Second, the tumor must be staged if possible by X-ray, CAT scan,
MRI or other types of scans to clarify its location within the
body, and to estimate the likelihood of effective curative or
palliative therapy. Staging of mesothelioma by x-ray measurements,
however, is difficult and often unreliable.
How are mesotheliomas treated? A treatment plan is devised
depending upon the mesothelioma type, aggressiveness, primary
location, and degree of local (rarely, distant) spread. The treatment
of pleural mesothelioma is difficult. Treatment with surgery,
radiation therapy or chemotherapy used alone or in combination
may be proposed, depending upon the potential benefits and risks
of each modality. Surgery is rarely used alone, but sometimes
suffices when only a small pleural patch of mesothelioma is detected,
thus allowing visually complete removal of the tumor. More often,
mesotheliomas of the left or right pleural cavity cannot be completely
removed without taking the entire lung (pneumonectomy) on the
same side as well. In such cases, radiation therapy and/or chemotherapy
is given postoperatively to help eradicate any residual mesothelioma
that may have escaped the surgeon.
The treatment of peritoneal mesotheliomas is even more problematic;
until recently no consistent treatment was available. At our institution,
peritoneal mesotheliomas have been managed in the experimental
setting with combined modality treatment consisting of extensive
(usually not complete) debulking surgery, followed by intraperitoneal
and systemic chemotherapy followed in turn by whole abdominal
radiation therapy.
Because mesotheliomas now represent less than one percent of cancers
and and are infrequently seen in the practice of most community
oncologists, finding the correct treatment can be very difficult.
Proper management of mesotheliomas often requires evaluation at
larger tertiary hospitals or Comprehensive Cancer Centers by specialists
in medical, surgical and radiation oncology with experience in
all aspects of the clinical care of mesothelioma patients, including
the newest experimental treatments.
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