Pleural plaque on chest x-ray may be the first and only indication that a person has been exposed to asbestos fibers. There are two types of pleural plaques – calcified and noncalcified. What’s the difference between calcified and noncalcified pleural plaques – and what’s the significance of each?
What Is Pleural Plaque?
Pleural plaques are white or yellow areas of thickening on the pleura, the special membrane that encases the lungs and chest wall. These plaques develop after a person is exposed to asbestos, but they don’t always appear right away. In fact, they may not show up on chest x-ray until forty years or more after exposure.
People who have had long-term exposure to asbestos, most commonly from construction and machinery environments, are more likely to develop pleural plaques, although there are cases where they occur in people who only had brief exposure to asbestos. These plaques are made of collagen tissue that's stimulated to grow by the body's immune response to the inhaled asbestos. The plaques commonly develop near the ribs, vertebrae or diaphragm. Studies have also shown a higher incidence of smokers among those with pleural plaques, although research is inconclusive whether smoking played a part in developing the plaques.
What is the Difference Between Calcified and Noncalcified Pleural Plaque?
Pleural plaques may be calcified or noncalcified, but only calcified plaques are readily seen on chest x-ray. Noncalcified plaque may not be visible at all unless it is very thick. On the other hand, even noncalcified parietal plaques can be seen on a chest CT scan.
Both calcified and noncalcified pleural plaques are a fairly certain sign of asbestos exposure, although not everyone exposed to asbestos develops pleural plaque. Fortunately, neither calcified nor noncalcified pleural plaques are cancerous, and the fact that a person has them does not mean they’re destined to develop asbestosis or mesothilioma, the two most serious diseases associated with asbestos exposure. It is also not clear whether having pleural plaques in the absence of other abnormalities puts a person at higher risk for mesothelioma.
Fortunately, neither calcified nor noncalcified pleural plaques cause symptoms of lung disease. On the other hand, people who have asbestosis almost always have pleural plaques, but they also usually have other signs of lung disease on chest x-ray such as pleural thickening. Pleural plaques are simply a sign of past exposure to asbestos and do not necessarily indicate disease. On the other hand, a person who has them should be closely monitored to ensure that symptoms of asbestosis or other lung problems do not develop.
The Bottom Line
The major difference between calcified and noncalcified pleural plaques is that one is easier to visualize on a chest x-ray than the other. Both types of plaques rarely cause symptoms, and one does no’t have a worse prognosis than the other. On the other hand, anyone who has pleural plaques or a history of exposure to asbestos needs close monitoring because of their past exposure to asbestos. It is also important for anyone with pleural plaques to avoid exposure to toxic fumes or cigarette smoke to reduce the risk of possibility of developing future lung problems.