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Pleural Plaques​

Pleural plaques are hardened areas on the linings surrounding the lungs caused by asbestos exposure. Most people with pleural plaques do not experience symptoms and may or may not develop mesothelioma or other asbestos-related diseases.


Medically Reviewed By:
Patricia Shelton, M.D.

Patricia Shelton

Medically Reviewed By:Patricia Shelton, M.D.

Asbestos exposure is the only proven cause of pleural mesothelioma, cancer of the thin linings, known as the pleura, surrounding the lungs. Mesothelioma is a latent disease, which means it develops decades after asbestos exposure has occurred. During the latency period, it is common for pleural plaques to form.

The presence of pleural plaques is also known as asbestos-induced benign pleural disease. They are considered a marker of asbestos exposure because they primarily occur in the presence of asbestos fibers in the lungs.

Pleural Plaques under microscope

What Are Pleural Plaques?

The National Institute for Occupational Safety and Health defines pleural plaques as hard, white, rubbery, fibrous lesions on the pleura, comprised of white blood cells and collagen. In some cases, they are especially hard due to calcification. They present with scalloped edges and a pattern resembling basket weaving.  They may be flat or nodular. They are not necessarily connected to each other.

In some cases, they also appear on the diaphragm, the thin muscle beneath the lungs.  According to the Jornal Brasileiro de Pneumologia, pleural plaques on the diaphragm strongly indicate that an asbestos-related disease may be present.

Although they are considered a marker of asbestos exposure, asbestos bodies are typically not found within pleural plaques.

What Are Pleural Membranes?

The lungs, heart, stomach, and testicles are surrounded by thin membranes known as mesothelia. The mesothelia surrounding the lungs are known as pleura or pleural membranes.  The pleural membranes are double membranes that have the capability of producing fluid. They function as cushioning sacs for the lungs.

The outer layer is known as the parietal pleura, and the inner layer is known as the visceral pleura. The parietal pleura is attached to the chest wall, a protective structure consisting of bone, tissue, and fat. The visceral pleura are inner membranes that cover the lungs and the internal structures of the lungs.

The production of fluid by the pleural membranes is important because it facilitates painless breathing by allowing the lungs to move easily as the chest expands and contracts upon inhaling and exhaling.

The space between the visceral and parietal pleura is known as a pleural cavity. The pleural membranes exist on both sides of the lungs with no connection between the two cavities. 

The other chest organs are protected by a separate structure known as the mediastinum. It is located in the middle of the lungs and protects the esophagus, heart, and major arteries.

The Location of Pleural Plaques

Pleural plaques generally occur on the parietal pleura. They most often occur bilaterally, which means they are present on both the left and right sides of the lungs. It is possible for these plaques to also appear on the diaphragm, which is the muscle located beneath the lungs.

What Are The Symptoms of Pleural Plaques?

Pleural plaques rarely cause symptoms. They are generally discovered incidentally during chest imaging tests or surgery.  Practitioners are often confounded by the seeming contradiction between these plaques and their patients’ lack of symptoms. Pleural plaques do not always spread and generally do not require treatment.

Do Pleural Plaques Increase the Risk of Developing Mesothelioma or Other Conditions?

Patients with pleural plaques are at a higher risk of developing asbestosis, lung cancer, or mesothelioma merely because they have been exposed to asbestos and not because of the plaques’ formation. A Swedish study of 1,596 men with pleural plaques concluded that pleural plaques indicate “significant exposure to asbestos.”

Whether the development of pleural plaques increases the risk of developing mesothelioma is controversial. A study of 4,240 workers published by the American Journal of Respiratory and Critical Care Medicine found that pleural plaques did not increase the risk of developing lung cancer.

The link between pleural plaques and mesothelioma is less clear. A study of 5,287 male mesothelioma patients published in the Journal of the National Cancer Institute found a statistically significant connection between pleural plaques and mesothelioma, indicating that pleural plaques may be an independent risk factor for the disease.

A German study published by the American Journal of Industrial Medicine in 2022 evaluated 2,439 workers with occupational asbestos-related diseases of the lung or pleura. It found a strongly increased risk of mesothelioma when pleural plaques were present but no association with lung cancer.

However, a 2011 review of the literature failed to find a connection between pleural plaques and mesothelioma or lung cancer, according to the French journal Revue des Maladies Respiratoires.

A study published by BMC Cancer in 2022 found that patients with lung cancer who also had pleural plaques had a significantly worsened prognosis.

Other Benign Conditions Affecting the Pleura

While pleural plaques are the most common pleural abnormality following asbestos exposure, the pleural membranes may also develop additional pathologies, including thickening of the pleura and pleural effusions—a fluid buildup in the pleural cavities.

Pleural Effusions

Pleural effusions are excess fluid in the pleural cavities. In some cases, this occurs without the presence of pleural plaques or thickening, and the mechanism behind it is unknown. However, pleural plaques or thickening can lead to this condition. Pleural effusions do not always cause symptoms, but breathing can become difficult with sufficient fluid buildup.

Diffuse Pleural Thickening

Also known as diffuse pleural fibrosis, diffuse pleural thickening is the thickening of the parietal or the visceral pleura, often due to scar tissue forming on the pleura. The extent of the thickening can range from very minor to severe, even to the point of restricting the lungs behind a thick wall of fibrous tissue. It resembles mesothelioma, but it is actually coarse bundles of collagen. These bundles tend to have a basket-weave pattern resembling pleural plaques. According to Clinical Medicine, diffuse pleural thickening may cause shortness of breath, but it often presents without symptoms.

Folded Lung Syndrome

Rounded atelectasis, also known as folded lung syndrome, is a form of pulmonary collapse in which part of the lung has folded onto itself. Surprisingly, according to the Polish Journal of Radiology, this condition often presents without symptoms.  In rare cases, coughing, shortness of breath, or chest pain may occur, but pleural lesions, asbestosis, or other co-occurring conditions could cause these symptoms. There is no consensus on how folded lung syndrome occurs. Some researchers theorize that pressure from fluid on the lung causes it. Another theory is that inflammation of the pleura caused by asbestos may cause it. Folded lung syndrome may also occur due to severe pleural thickening or when pleural plaques develop on the visceral pleura.


Asbestosis is the scarring of the lungs, which may or may not occur simultaneously with pleural plaques. The only established connection between pleural plaques and asbestosis is that they both point to a history of asbestos exposure. Both conditions are non-cancerous, but they appear to develop independently of one another.

What Causes Pleural Plaques?

Asbestos fibers seem to have an affinity for the pleura. However, the exact pathology behind pleural plaques is uncertain. According to ClinMed International Library, one possible theory is that as the lungs attempt to clear asbestos fibers, the fibers enter the bloodstream and get transported throughout the body. They then return to the lungs and are ultimately deposited in the parietal pleura. Another theory is that rather than entering the bloodstream, changes in pressure gradients inside the lungs caused by inflammation may result in the fibers moving to the visceral pleura via the capillaries.

How Long Does It Take Pleural Plaques to Form?

A study published by the Journal of Environmental Health found that the latency of pleural plaques was between five and ten years after exposure, although this can vary. The exact latency of pleural plaques is difficult to determine because they are often diagnosed long after formation due to their asymptomatic nature.

How Common Are Pleural Plaques in People Exposed to Asbestos?

The prevalence of pleural plaques after asbestos exposure is not well understood. According to a study by Hammar SP, as many as 80 percent of workers with significant asbestos exposure will develop pleural plaques visible on chest X-rays, compared to 0.5 to eight percent of the unexposed population.

However, according to another medical journal, the Revista Brasileira De Medicina Do Trabalho, the occurrence ranges widely between three and 58 percent of workers exposed to asbestos. Although the prevalence is unclear, the Journal of Environmental Health study did find a correlation between the following:

In essence, the incidence of pleural plaques increases as the time since initial asbestos exposure increases and with higher levels of asbestos exposure.

How Are Pleural Plaques Diagnosed?

Pleural plaques are usually diagnosed by accident while screening for other conditions or during surgery for another condition. Imaging screenings that may result in the discovery of pleural plaques include chest X-rays, CT scans, and MRIs.

What Should You Do If You Have Been Diagnosed with Pleural Plaques?

Learning that you have pleural plaques can be frightening, but it does not mean you will go on to develop a disease. Studies have yet to prove that the development of pleural plaques increases the risk of developing mesothelioma beyond that of others exposed to asbestos. Pleural plaques do indicate a history of asbestos exposure, so it is important to ensure they are documented in your medical history and that your health care providers are aware of your history of asbestos exposure. Annual screening may ensure an early diagnosis of mesothelioma or lung cancer should they develop. The American Cancer Society reports that low-dose CT scans can benefit those with a higher risk of developing lung cancer. Dr. Robert Cameron, a world-renowned pleural mesothelioma scientist, physician, professor, and head of the mesothelioma program at the West Los Angeles VA Medical Center, recommends completing a chest X-ray and baseline CT scan on an annual basis if you have a history of asbestos exposure.

Can I File a Lawsuit for Pleural Plaques?

Pleural plaques generally do not require medical treatment, nor do they cause symptoms. Thus, they do not meet the legal definition of an injury. Without an injury, there are no grounds for a lawsuit.

However, the presence of pleural plaques can be important evidence in a lawsuit involving lung cancer. Lung cancer is the most common asbestos-related disease, but other factors, such as smoking, radon, and exposure to other airborne toxins, can also cause it. As a result, it is necessary to prove that asbestos exposure is the cause.

While it may be possible to do so through the process of elimination, the presence of pleural plaques, in addition to lung cancer, is strong evidence for a connection between lung cancer and asbestos exposure.

If you have developed an asbestos-related illness, contact the Lanier Law Firm today to learn how you may be able to recover substantial compensation.

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