Characteristics

• Asbestos-related pleural plaques represent focal areas of fibrotic response in the visceral pleura to previous exposure to inhaled asbestos fibres at least 8–10 years before. Classically, they calcify (approximately 50%). Both the presence of plaques and their calcification increase with time. They spare the costophrenic angles and lung apices. In their own right they have no malignant potential; however, in some patients, asbestos exposure can lead to pulmonary fibrosis, lung cancer and mesothelioma.

Clinical features

• Asbestos plaques are asymptomatic. Any chest symptoms should alert the clinician to the potential complications of asbestos exposure.

Radiological features

• CXR – focal areas of pleural thickening (< 1 cm). They are usually bilateral and may be multiple. Plaques are more visible when they calcify and calcified plaques have a thicker peripheral edge than central portion. When they are seen en-face they have an irregular ‘holly leaf’ appearance. Non-calcified plaques seen en-face can give a patchy density to the lungs. There should be no lymphadenopathy.

• They are associated with rounded atelectasis or pseudotumours. On the CXR these look like peripherally based round nodules mimicking lung neoplasms. On CT imaging they demonstrate a rounded area of lung abutting an area of pleural thickening, with a swirl of vessels (tail) leading to the peripheral-based lesion. They are completely benign and should be recognised to avoid further invasive investigations.

• Occasionally the pleural thickening can be diffuse, restricting lung function and mimicking mesothelioma.

Differential diagnosis

• There are few conditions which have a similar appearance.

• Previous history of TB or haemorrhagic pleural effusions can give a similar picture (more often unilateral).

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