The commonly encountered asbestos-related conditions and diseases mainly relate to the lungs. These include pleural effusion, pleural plaques, and diffuse pleural thickening — collectively referred to as benign pleural disease — as well as asbestosis, lung cancer, and malignant pleural mesothelioma.
In this post we focus on the several types of pleural disease associated with asbestos exposure. For the basic facts we will draw upon an article, “Asbestos: When the Dust Settles—An Imaging Review of Asbestos-related Disease”, which was published in the October 2002 edition of RadioGraphic medical journal.
As an introduction, while asbestosis, asbestos lung cancer, and mesothelioma may be more well-known asbestos-related medical conditions, pleural disease is the most commonly encountered asbestos-related disease. Pleural disease can occur as pleural effusion, plaques, or thickening, as well as atelectasis.
From the above mentioned RadioGraphic medical journal article:
Benign pleural effusions are thought to be the earliest pleural-based phenomenon (1) (Fig 1)…. They usually occur within 10 years of exposure (12), but they can also develop much later…. The development of effusions is thought to be exposure-dependent (11), but they can occur even after minimal exposure (13) and can be dependent on occupation (11).
The most common manifestation of asbestos exposure is pleural plaques, which are discrete areas of fibrosis that usually arise from the parietal pleura but may arise from visceral pleura. They tend to occur 20–30 years after exposure (1). The classic distribution of plaques seen on chest radiographs is the posterolateral chest wall between the seventh and tenth ribs, lateral chest wall between the sixth and ninth ribs, the dome of the diaphragm (virtually pathognomonic), and the mediastinal pleura (1,14) (Fig 2).
Diffuse Pleural Thickening
Diffuse pleural thickening is less specific for asbestos exposure because other causes of exudative effusions can lead to it. It results from thickening and fibrosis of the visceral pleura, which leads to fusion with the parietal pleura (Fig 7), and is preceded by benign pleural effusion (1) (Fig 8). Histologically, there is similarity between pleural thickening and plaques, except that fusion of the pleural layers is suggestive of more intense inflammation (22).
The pathogenesis of round atelectasis is not certain, but it is thought to be due to an inflammatory reaction and fibrosis in the superficial layer of the pleura. As the fibrous tissue matures, it contracts, causing pleura to fold into the lung, which in turn causes atelectasis (28). Asbestos-related round atelectasis is also known as asbestos pseudotumor or Blesovsky syndrome.
The typical chest radiographic appearance is of a rounded peripheral “mass” with or without lung distortion (Fig 10a). Pleural thickening is usually seen. The CT features are of a round or oval mass that abuts the pleura, a “comet tail” of bronchovascular structures going into the mass, and thickening of the adjacent pleura (1,29) (Figs 10b, 11).
The medical significance of a diagnosis of pleural disease is that it often indicates there has been a significant past exposure to asbestos and, as such, it probably means that there is an increased risk of developing asbestosis, lung cancer, or mesothelioma for that person.
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