Pleural plaques are benign, meaning they are not cancerous. Furthermore, they cannot become cancerous over time. In nearly every case, there are no symptoms, but some patients describe pain or an uncomfortable grating sensation as they breathe.
They can develop on both layers of the pleura, a thin membrane that surrounds the lungs and aids in breathing. They most commonly develop on the parietal pleura, which lines the inside of the rib cage, but can also affect the visceral pleura, which lines the lungs.
Additionally, pleural plaques can grow on the diaphragm, the primary muscle used for respiration. The plaques can calcify over time, but they do not usually cause long-term health problems.
Causes of Pleural Plaques
Pleural plaques are almost exclusively caused by exposure to asbestos, but having the condition does not necessarily mean you will develop a more serious asbestos-related disease such as asbestosis or mesothelioma.
However, because the presence of plaques suggests a significant past exposure to asbestos, mesothelioma or lung cancer may arise later in life.
Some studies suggest fibrous thickening of the pleura may increase a patient’s risk for developing pleural mesothelioma, but the topic remains controversial. Contradictory studies show a patient’s risk for other asbestos-related conditions is not affected by a diagnosis of pleural plaques.
Instead, they argue doctors should calculate a patient’s risk based on the level and duration of asbestos exposure and how much time has passed since the initial exposure.
How Do They Form?
When people are exposed to asbestos, inhaled fibers can accumulate in the lining of the lungs and irritate the lung tissue. It is believed fibers reach the pleural space through the lymphatic system.
A leading theory suggests asbestos fibers cause an immune response that summons special lung cells called pleural macrophages. These cells can trigger a chain of events that leads to fibrosis, in which specialized cells replace normal, healthy lung tissue with scar tissue made of collagen fibers.
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Pleural Plaque Development
Pleural plaques slowly develop and grow as fibrotic scar tissue accumulates. 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 also develop pleural thickening, which involves more extensive fibrous thickening. Because pleural thickening affects a larger area, it can prevent the lungs from fully expanding and cause shortness of breath.
Risk, Prevalence and Diagnosis
Often, pleural plaques do not show up until decades after exposure to asbestos. Most experts agree the risk is dose dependent, meaning the risk increases with the level of asbestos exposure and time elapsed since first exposure.
Despite this relationship, low levels of asbestos exposure can still cause pleural plaques to arise.
In a 2013 study in France, doctors screened asbestos-exposed workers using computed tomography (CT) scans.
The study, published in the Journal of the National Cancer Institute, identified pleural plaques in 7.4 percent of patients exposed to asbestos between one and nine years. More than 50 percent of patients with 40 or more years of asbestos exposure developed plaques.
A follow-up study discovered 17 cases of pleural mesothelioma were diagnosed in the cohort between the date of the CT scan and March 31, 2011. The mean age of patients with pleural plaques who later developed mesothelioma was 66.6 years. All mesothelioma diagnoses were linked to occupational asbestos exposure.
Discovery Through X-ray
Most incidences are discovered after an X-ray that displays thickened nodular edges resembling a holly leaf. In certain locations, the condition can be difficult to identify via X-ray. Pleural plaques that are calcified appear more pronounced.
Diagnoses with CT Scan
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 percent of cases, a CT scan can correctly identify patients who have this condition.
When pleural plaques are first discovered, your health care provider will carefully 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.
Treatment and Preventing Further Damage
Because pleural plaques are noncancerous and the majority of patients do not experience a loss in lung function, treatment is not necessary. However, you can prevent further damage by eliminating any pathways of asbestos exposure and by quitting smoking. Your doctor can give you advice to help with smoking cessation.
Although pleural plaques may not place you at a higher risk of developing a more serious asbestos-related disease, the asbestos exposure that caused the plaques does. Therefore you should always notify your doctor if you experience symptoms such as breathlessness, persistent cough, chest pain or coughing up blood. If breathing does become an issue, your doctor can perform a variety of tests and offer treatments and refer you to a specialist.
6 Cited Article Sources
Agency for Toxic Substances and Disease Registry. (2010). Asbestos Toxicity: What Tests Can Assist with Diagnosis of Asbestos Toxicity?
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Gevenois, P.A. et al. (1998). Asbestosis, pleural plaques and diffuse pleural thickening: three distinct benign responses to asbestos exposure. European Respiratory Journal, 11.
Retrieved from: http://www.erj.ersjournals.com/cgi/reprint/11/5/1021.pdf
National Heart, Lung and Blood Institute. (2011, May 1). What Are Asbestos-Related Lung Diseases?
Retrieved from: https://www.nhlbi.nih.gov/health/health-topics/topics/asb/
The Industrial Injuries Advisory Council. (2009, June). Position Paper 23: Pleural Plaques.
Retrieved from: http://iiac.independent.gov.uk/pdf/pos_papers/pp23.pdf
Pairon, J.C. et al. (2013, February 20). Pleural Plaques and the Risk of Pleural Mesothelioma.
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- Weerakkody, Y. and Gaillard, F. (n.d.). Pleural Plaque. Retrieved from: http://radiopaedia.org/articles/pleural-plaque
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Last Modified April 10, 2019