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Pleural Plaques

Pleural plaques are areas of benign thickening of the lining of the lungs that develop after prolonged asbestos exposure. Treatment is often unnecessary and patients can live for many years without any serious health problems.

Pleural plaques, sometimes referred to as hyaline pleural plaques, are a common sign of asbestos exposure. Unlike other asbestos-related diseases like mesothelioma or asbestos lung cancer, pleural plaques are always considered non-cancerous or benign. In many cases, the condition may show no symptoms at all and will require little to no medical intervention. There is debate, however, around whether or not patients diagnosed with pleural plaques have a higher chance of developing pleural mesothelioma or another asbestos-related pleural disease at some point.

Asbestos Exposure and Pleural Plaques

Researchers have found that pleural plaques are rather exclusively caused by exposure to asbestos, and most common among workers exposed to the toxin on the job. In some cases, even those exposed to asbestos fibers for a short period of time also later developed pleural plaques.

It is recognized as the most common asbestos-related disease, with one study even noting that upwards of 60% of pleural plaque cases may go undiagnosed. A large study of over 13,000 asbestos workers observed the instances of pleural plaques and pleural thickening from 2003 to 2011, and also noted the prevalence of future mesothelioma diagnoses. Overall, about 1,100 patients were found to have pleural plaques, or nearly 21% of patients. During this time period, 17 patients were ultimately diagnosed with pleural mesothelioma. Other similar studies have found an even higher prevalence of pleural plaques among asbestos workers, with one study even finding about 50% of the participants had developed pleural plaques.

Pleural plaques may develop in the parietal pleura, the outer membrane of the lung lining that also attaches to the chest wall, or the diaphragm after ingestion or inhalation of asbestos fibers. Researchers believe the fibers may then reach the lungs and pleural space through the lymphatic system. The fibers can easily become lodged in the lung lining, causing irritation and inflammation over time. The plaques develop as localized thickening of the pleura over time as scar tissue builds.

In general, researchers have observed an average latency period of 20 years before pleural plaques may develop, though some patients have experienced the condition much sooner.

Diagnosing Pleural Plaques

Detecting pleural plaques can be difficult because the condition doesn’t generally cause many or any symptoms at all. In very rare cases, some patients have experienced some chest pain, a cough, or slight difficulty breathing at times. Overall, though, doctors have noted that pleural plaques do not have much influence on lung function or cause many health problems.

Since pleural plaques are generally asymptomatic, many diagnoses occur incidentally. However, since the condition is almost always linked to asbestos exposure, it may be easier to diagnose in patients aware of past exposure and having regular screenings for any signs of disease. Specifically, pleural plaques are described as localized fibrous deposits that thicken the lung lining. They develop as white lesions with a rubbery consistency, though may become calcified or hardened over more time.

Pleural plaques are typically identified through imaging scans. Commonly, the condition may first be identified in a chest radiograph or X-ray that shows thickened areas of the lung with concrete edges, which some researchers have noted can look a bit like a holly leaf. The impacted areas of the lung can be even clearer if the patient has calcified pleural plaques.

A CT scan will be able to create a clearer image of the pleural plaques and their extent on the lung. In general, doctors tend to prefer this type of imaging test as it is much more sensitive and specific than a chest x-ray, meaning it can detect these asbestos lung diseases even in their early stages. On the scan, health care professionals will be able to see better defined areas of thickening, which are often described as nodular, linear structures. Some researchers have even noted these areas resemble a basket weave.

Because pleural plaques are identified as thickened areas of the lung, some studies refer to the condition as localized pleural thickening for this reason. As such, pleural thickening and pleural plaques may sometimes be mistaken in diagnosis or the conditions may even be co-occurring in a patient. While pleural plaques are benign, however, diffuse pleural thickening can cause more severe health issues and may even be a sign of a more dangerous diagnosis like mesothelioma. With this in mind, it’s important for doctors to take care in properly differentiating these diagnoses.

Monitoring Pleural Plaques After Diagnosis

It’s uncommon for patients to require any treatment for a pleural plaques diagnosis. This is because the areas of thickening often stay localized and don’t cause many symptoms, if the patient experiences any symptoms at all.

While the condition doesn’t generally require treatment on its own, sometimes doctors may recommend pulmonary function tests or lung function tests to ensure the condition hasn’t contributed to the development of other asbestos-related conditions like pleural effusions or pleural thickening. These tests will observe lung capacity and how oxygen reaches the bloodstream.

Doctors may also recommend that patients follow a healthier lifestyle to keep lung function strong, which can include following a healthy diet, a certain exercise routine, and quitting smoking. Research has been mixed on whether or not smoking may contribute to worsening pleural plaques or other asbestos-related diseases. But either way, quitting will help with overall lung health.

Pleural plaques may also put patients at a higher risk of pleural mesothelioma. Monitoring efforts like these lung function tests, as well as keeping an open dialogue with your doctor about any other symptoms that may arise, can ensure that the aggressive cancer is detected early if it should develop.

Author: Linda Molinari

Editor in Chief, Mesothelioma Cancer Alliance

Linda Molinari

Bianchi C, Brollo-A, et al. Hyaline pleural plaques and asbestos exposure. Centers for Disease Control, National Institute for Occupational Safety and Health, DHHS (NIOSH) Publication No. 90-108, 1990 Nov; (Part II):919-923.

Gevenois PA, de Maertelaer V, et al. Asbestosis, pleural plaques and diffuse pleural thickening: three distinct benign responses to asbestos exposure. European Respiratory Journal. 1998; 11: 1021–1027 doi: 10.1183/09031936.98.11051021.

Kishimoto T, Morinaga K, et al. The prevalence of pleural plaques and/or pulmonary changes among construction workers in Okayama, Japan. American Journal of Industrial Medicine. 2000 Mar;37(3):291-5.

Maxim D, Niebo R, et al. Are pleural plaques an appropriate endpoint for risk analyses? Inhalation Toxicology. 2015. 27 (7): 321-334.

Pairon JC, Laurent F, et al. Pleural Plaques and the Risk of Pleural Mesothelioma. Journal of the National Cancer Institute,. 20 February 2013. 105(4): 293–301. doi: 10.1093/jnci/djs513

Paris C, Martin A, et al. Modelling prevalence and incidence of fibrosis and pleural plaques in asbestos-exposed populations for screening and follow-up: a cross-sectional study. Environmental Health. 2008; 7: 30. doi: 10.1186/1476-069X-7-3

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