Pleural mesothelioma is the most prevalent of all
types of mesothelioma.
It affects the soft tissue surrounding the lungs known as the pleura
or pleural membrane. Mesothelioma tumors can develop in multiple
locations throughout the body, but they originate from the pleura in
approximately 75 percent of all cases. In each case, cancer forms in
the mesothelium, a tissue membrane that protects various organs and
body cavities.
Pleural mesothelioma is typically caused by
occupational exposure to airborne asbestos fibers.
Because this exposure is frequently in male-dominated industries,
around 80 percent of all pleural mesothelioma patients are men. Once
inhaled into the lungs, needle-like asbestos fibers migrate to the
pleural membrane, where the body cannot easily get rid of them. Fibers
irritate the pleura, which can result in chronic inflammation and
scarring. Infrequently, this causes pleural mesothelioma.
Over an extended period of time – usually three or more decades –
asbestos triggers genetic changes in the pleural cells. If the cells
become cancerous, they begin to divide uncontrollably, forming tumors
that reduce lung capacity and generate excess fluid buildup between the
pleural layers.
The overall outlook for pleural mesothelioma patients is poor. This
is because symptoms do not usually arise until more advanced stages of
cancer where curative surgery is no longer an option. However, an early
diagnosis facilitates the most effective treatment options, potentially
improving a patient's outlook and
life expectancy.
The Anatomy and Function of the Pleura

The pleural lining is composed of two layers that provide protection
and support for the lungs and other vital structures of the chest. It
also produces a lubricating fluid for the cavity between the two layers
to aid the expansion and contraction of the lungs as we breathe. The
outer layer, the parietal pleura, lines the entire chest cavity. The
inner layer, or visceral layer, covers the lungs.
It is not uncommon for mesothelioma to affect both layers of the
pleura. Pleural mesothelioma generally develops in one layer of the
pleura and rapidly invades nearby locations such as the diaphragm,
chest wall or lung. If the cancer reaches the lymph nodes, it can
metastasize, or spread, to distant locations in the body.
Pleural Mesothelioma Symptoms
When trapped asbestos fibers cause healthy pleural cells to become
cancerous, tumors form and the pleural membrane slowly thickens. The
thickening can cause
pleural effusion,
an excess buildup of fluid in the space between the pleural layers.
This fluid puts pressure on the lungs, resulting in chest pain and the
impairment of normal breathing. These complications are largely
responsible for the symptoms of pleural mesothelioma, which include:
- Persistent dry or raspy cough
- Coughing up blood (hemoptysis)
- Shortness of breath (dyspnea)
- Pain in the lower back or rib area
- Painful breathing
- Development of lumps under the skin on the chest
- Difficulty with swallowing (dysphagia)
- Night sweats or fever
- Unexplained weight loss
- Fatigue
Although someone in a later stage of pleural mesothelioma experiences
weight loss and fatigue, less than 30 percent of patients experience
these symptoms before a diagnosis or during an early stage of the
disease. During an initial consultation with their doctor, more than 60
percent of patients experience chest pain and breathlessness related
to pleural effusion.
Learn more about pleural mesothelioma symptoms
Pleural Mesothelioma Diagnosis
As with other types of the disease, pleural mesothelioma can be
difficult to diagnose, even for specialists. Symptoms usually do not
arise until long after an initial exposure to asbestos. And because
many respiratory conditions provoke similar symptoms, pleural
mesothelioma is often mistaken for less-threatening diseases like
influenza and pneumonia. Further, it is challenging for doctors to
distinguish between pleural mesothelioma and
adenocarcinoma, a common form of lung cancer.
Diagnostic Imaging
X-rays or CT-Scans are often used to diagnose pleural mesothelioma.
A pleural mesothelioma diagnosis can be made partly on the basis of
symptoms, but additional diagnostic tests are often needed to confirm
the presence of cancer. To achieve the best treatment options and
patient outlook, an early diagnosis is crucial. Following a medical and
occupational history review and a physical examination, patients
typically undergo imaging tests that identify potentially cancerous
tumors. Conventional
chest X-rays can reveal pleural effusions and pleural-based masses in some cases, but
CT scans provide more advanced images that often reveal evidence of asbestos exposure.
With the introduction of the
PET scan
in the early 1960s, doctors could better distinguish between benign
(non-cancerous) and malignant pleural growths. Additionally, PET scans
can detect signs of cancerous spread to the lymph nodes that CT scans
often miss, a benefit that is particularly useful for mesothelioma
staging. A promising combination of both technologies, known as PET-CT
imaging, emerged in 2000. Some experts contend that a PET-CT scan can
more accurately predict a patient’s response to chemotherapy than PET
and CT scans given alone, but further studies must be done to confirm
this with certainty.
Cytology and Biopsies
Cytologies and biopses help diagnose mesothelioma with higher confidence.
While recent advances in imaging have markedly improved the
diagnostic process, more invasive procedures are usually needed to
diagnose mesothelioma with a high level of confidence. One such
procedure is
thoracentesis,
in which a hollow needle is inserted into the lungs to collect pleural
fluid. Using cytologic analysis to inspect the cell samples, doctors
look for biomarkers that indicate the presence of cancer, such as
epithelial membrane antigen (EMA), calretinin and WT1. Experienced
physicians can use cytologic analysis to make an accurate diagnosis in
80 percent of mesothelioma cases.
Sometimes, however, results are inconclusive or pleural fluid is absent entirely. In these cases, doctors perform
biopsies
to collect pleural tissue samples. Color stains are added to the
samples to help doctors visualize cellular structures. One popular
biopsy method is
fine needle aspiration, but researchers have found that
thoracoscopy
is far more likely to yield positive results. A thoracoscopic biopsy
produces an accurate diagnosis in 98 percent of mesothelioma patients.
The current gold standard for diagnosing pleural mesothelioma involves
the examination of stained tissue samples under an electron microscope.
If a series of tests or biopsies can confirm the presence of
mesothelioma, doctors develop a treatment plan based on the results.
Learn more about pleural mesothelioma diagnosis
Pleural Mesothelioma Treatment
Historically, doctors have managed pleural mesothelioma with
traditional cancer treatments like surgery, chemotherapy and radiation
therapy. Depending on how far the patient’s mesothelioma has
progressed, these therapies can be either curative or palliative.
Although pleural mesothelioma patients are rarely diagnosed early
enough to qualify for curative surgery, many palliative treatments
exist that can alleviate painful symptoms, improve quality of life and
significantly extend survival. Researchers are also evaluating several
alternative treatments like
immunotherapy and
gene therapy, which once perfected could one day become standard mesothelioma therapies.
Surgery
Surgery continues to serve as a primary treatment option for pleural mesothelioma patients. One common procedure is
pleurectomy/decortication (P/D), which involves surgical removal of the tumor and affected pleura. A more aggressive surgical option,
extrapleural pneumonectomy (EPP)
aims to safely remove an entire lung, the diaphragm and the
pericardium, a protective membrane that lines the heart. Only a fraction
of patients have lung function adequate enough to qualify for EPP, and
one large, multi-facility analysis found that P/D offers better
outcomes than EPP with fewer risks.
Chemotherapy
One of the most common palliative mesothelioma treatments is
chemotherapy,
which uses one or more drugs to kill cancer cells and decrease the
size of tumors. While recent advancements have improved patient
responses to chemotherapy, success rates have been low overall. Roughly
15 to 20 percent of mesothelioma patients will experience a notable
reduction in tumor size after chemotherapy.
However,
mesothelioma clinical trials
combining several chemotherapy drugs in one treatment have
demonstrated great potential. One multicenter phase 3 study, for
example, found that a combination of pemetrexed and
cisplatin
prolonged patients’ overall median survival by 2.8 months compared to
patients treated with cisplatin alone. 41 percent of patients treated
with a pemetrexed/cisplatin regimen experienced tumor shrinkage of at
least 50 percent. While a combination of chemotherapy drugs that cures
pleural mesothelioma has yet to be discovered, this is a primary goal
of countless researchers currently involved in clinical trials.
Radiation Therapy
Pleural mesothelioma often resists
radiation therapy.
In this treatment, doctors administer targeted radiation that destroys
cancer cells and decreases tumor size. Although it is a poor curative
option, radiation therapy can be quite effective for managing symptoms
like chest pain. One of the most successful radiotherapy techniques is
called intensity-modulated radiotherapy. Usually given to patients in
low-dose intervals after a radical surgery like EPP, this technique
prevents cancer recurrence in many cases. While effective at preventing
the cancer from returning to areas where radiation is administered,
spread to distant sites remains a challenge.
Multimodal Therapies
While there is no universally accepted course of treatment for
pleural mesothelioma, the majority of experts agree that survival can be
greatly improved when several treatments are combined. This is known
as
multimodal therapy,
and researchers constantly experiment with surgery, chemotherapy and
radiation therapy to uncover the most effective combination and timing
for these treatments. In one example of a multimodal pleural
mesothelioma treatment, doctors first perform extrapleural
pneumonectomy surgery. Radiation therapy is then administered to reduce
the risk of local cancer recurrence, and distant spread is prevented
with chemotherapy.
Learn more about pleural mesothelioma treatments
Pleural Mesothelioma Prognosis

After the diagnostic process, doctors will analyze their
mesothelioma patient’s clinical data to predict the expected course and
outcome for the disease. This prediction is known as the patient’s
prognosis.
Past studies indicate that average survival ranges from four to 18
months, but many factors can significantly affect the prognosis of
pleural mesothelioma patients. The most substantial factors include the
current
stage
of disease and the overall health of the patient. Staging is a system
doctors use to describe how far the mesothelioma has advanced, so
diagnosis at an early stage offers a better prognosis. And patients in
good health who can still perform normal daily tasks tend to respond
better to the demands of treatment.
Other important prognostic factors include the patient’s age, sex
and smoking history. Survival is generally better for female patients,
non-smokers and patients younger than 55. The cancer’s
histology,
or the cellular structure of the tumor, can also strongly influence
prognosis. Accounting for 50 to 70 percent of all cases, a subtype
known as
epithelial mesothelioma offers the most hopeful prognosis. Patients with epithelial mesothelioma respond best to treatment, and other subtypes like
sarcomatoid and mixed mesothelioma are associated with poorer survival.
Providing mesothelioma patients with an accurate prognosis can be a
challenging task for doctors. Not only is pleural mesothelioma a rare
disease, but it is also uncommon for patients to be diagnosed at an
early stage. Because most patients don’t qualify for surgery and an
operation is required for accurate staging, survival data for stage I
and stage II is limited.
Overall, around 40 percent of pleural mesothelioma patients survive
one year after a diagnosis. Approximately 20 percent survive for two or
more years, and 10 percent will be alive five years later. It is
important, however, to understand that these statistics are drawn from
large samples of patients. Each individual case is unique, so survival
statistics should only serve as general guidelines.
Patients can work with the nation’s
top mesothelioma specialists
to improve their prognosis and discuss treatment options to extend life
expectancy. Many mesothelioma survivors have turned to a dynamic
treatment plan that unites traditional and alternative medicine to
boost prognosis.
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