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.
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.
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?
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 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
Folded Lung Syndrome
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?
How Long Does It Take Pleural Plaques to Form?
How Common Are Pleural Plaques in People Exposed to Asbestos?
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.