Pleural Plaques and Asbestos

Fact Checked

Pleural plaques are areas of hyalinized collagen fibers and form in the pleura. They are the most common sign of asbestos exposure. Imaging scans may show pleural plaques 20 to 30 years after long-term inhalation of asbestos fibers. In some patients, the latency period is less than 10 years.

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What Are Pleural Plaques?

X-ray of calcified asbestos pleural plaques
Close-up X-ray of calcified asbestos pleural plaques. The translucent white areas behind the rib cage show the pleural plaques.

Pleural plaques are an asbestos-related disease, but they are not cancerous.

However, pleural plaques may be an indicator of a higher risk for cancer such as pleural mesothelioma or asbestos lung cancer. But they do not directly lead to cancer.

After prolonged exposure to asbestos, pleural plaques can develop on both layers of the pleura, which is the thin membrane that surrounds the lungs and envelops the inside of the chest.

The majority of people with pleural plaques do not show obvious symptoms. But some patients describe pain or an uncomfortable, grating sensation as they breathe.

Pleural plaques are also called hyaline pleural plaques because the growths are composed of hyaline tissues

What Causes Pleural Plaques?

Pleural plaques are caused almost exclusively by exposure to asbestos. However, having the condition does not necessarily mean you will develop mesothelioma.

Inhaled asbestos fibers can accumulate in the lining of the lungs and irritate the lung tissue. Researchers believe fibers reach the pleural space through the lymphatic system.

One theory suggests asbestos fibers cause an immune response that summons special lung cells called pleural macrophages. These cells can trigger a chain of events beginning with inflammation and ending with fibrosis.

Fibrosis is the process through which specialized connective tissue replaces normal, healthy lung tissue with collagen fibers. These fibrous areas are sometimes called scar tissue.

Quick Fact:

In 20% of cases, pleural plaques become calcified. As calcium deposits build, the scar tissue hardens. Calcified pleural plaques rarely inhibit lung function and cause patients to have trouble breathing.

Where Do Pleural Plaques Develop?

Pleural plaques most commonly develop on the parietal pleura, which lines the inside of the rib cage. They also can form on the visceral pleura, which lines the lungs.

Additionally, these hyaline growths can occur on the diaphragm, which is an important breathing muscle.

What Are the Symptoms of Pleural Plaques?

Pleural plaques do not usually cause any symptoms.

While doctors traditionally believed they did not affect a patient’s lung function, recent evidence shows they sometimes cause a minimal decrease in total lung capacity and other measures of lung function.

Asbestos-exposed patients with pleural plaques may develop pleural thickening, which involves more extensive fibrous growth. Because pleural thickening affects a larger area, it can prevent the lungs from fully expanding and cause shortness of breath.

You should always notify your doctor if you experience symptoms such as breathlessness, persistent cough, chest pain or coughing up blood, which may be signs of a more serious undiagnosed condition.

If breathing does become an issue, your doctor can perform a variety of tests, offer treatments and refer you to a specialist if necessary.

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How Are Pleural Plaques Diagnosed?

Pleural plaques are diagnosed using imaging scans.

But for many people, pleural plaques are diagnosed by accident. Patients may be undergoing chest imaging for other reasons, and the plaques are simply caught by chance.

Discovery Through X-ray

Most incidences are discovered after an X-ray shows areas around the lungs with thickened nodular edges resembling a holly leaf. In certain locations, the condition can be difficult to identify via X-ray.

Calcified pleural plaques appear as translucent white deposits on the lungs in X-ray imaging scans.

Diagnosis with CT Scan

A CT scan is the preferred method for diagnosing this condition, as it can identify plaques anywhere in the chest, even if they are not calcified. In 95% to 100% of cases, a CT scan can correctly identify patients who have this condition.

When pleural plaques are first discovered, your health care provider will evaluate your history of asbestos exposure and check for other signs of asbestos-related disease. If you are later diagnosed with an asbestos-related disease, your doctor will create a treatment plan unique to you and your diagnosis.

Quick Fact:

Doctors typically diagnose this condition using a chest X-ray or CT scan. Because it rarely causes symptoms, they usually find it incidentally after performing an imaging scan for an unrelated reason.

Prevalence and Risk of Developing Pleural Plaques

It is challenging to estimate the exact prevalence of pleural plaques in people exposed to asbestos because most people with past exposure are not routinely screened for these fibrous pleural changes.

A 2017 study examined 1,512 CT scans, and researchers noted 76, or 5.1% of the images, indicated the presence of pleural plaques. In 13 of these 76 patients with pleural plaques, the original CT scan was performed due to suspicion of prior asbestos exposure.

These findings suggest pleural plaques are not common in the general public.

In contrast, a 2018 Japanese study of 2,132 asbestos-exposed workers found pleural plaques on CT scans of 89.4% of the group.

This strongly supports the connection between asbestos exposure and pleural plaques. It also suggests that with enough inhalation of asbestos fibers, nearly everyone eventually develops pleural plaques.

How Are Pleural Plaques Treated?

Treatment is not necessary because pleural plaques are noncancerous and the majority of patients do not experience a loss in lung function.

However, these steps can prevent further damage:

  • Quit smoking: Ask your doctor for help with a smoking cessation program.
  • Avoid further asbestos exposure: Avoid asbestos. If you must work around it, use personal protective equipment such as a respirator and disposable coveralls.
  • Minimize exposure to air pollution: If you live in an area with wildfires and other sources of heavy air pollution, heed warnings to stay indoors when pollution levels are highest.

Are Pleural Plaques Related to Cancer?

Some research suggests fibrous thickening of the pleura does increase a patient’s risk for developing pleural mesothelioma. However, contradictory studies show a patient’s risk for other asbestos-related conditions is not affected by a diagnosis of pleural plaques.

When assessing whether a person with hyaline plaques is at increased mesothelioma risk, most cancer experts recommend assessing each person based on their unique cancer risk factors.

The doctor may estimate a patient’s mesothelioma or lung cancer risk based on the level and duration of asbestos exposure and how much time has passed since the initial exposure to inhaled asbestos fibers.

Some plaques can calcify, or harden over time, but they do not indicate cancer and do not cause long-term health problems for most people.

Although pleural plaques may not place you at a higher risk of developing a more serious asbestos-related disease such as asbestosis, the asbestos exposure that caused the plaques does.

Be sure your primary care provider knows about your past asbestos exposure and notes this in your medical chart.

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Oncology Medical Writer

Suzanne Dixon is a registered dietitian, epidemiologist and experienced medical writer. She has volunteered with the National Cancer Policy Forum, Oncology Nutrition Dietetic Practice Group, American Institute for Cancer Research, American Society for Clinical Oncology, The National Academies of Sciences, Engineering, and Medicine. The New York Times and Time Magazine also have reviewed her cancer patient resources.

Walter Pacheco, Managing Editor at Asbestos.com
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Last Modified July 16, 2019

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