Pleural Plaques: Diagnostic Problems and Significance

Abstract

Hyaline plaques of the parietal pleura are diagnosed by inspection. They are detectable at autopsy, thoracotomy or thoracoscopy, or on computed tomogra phy (CT) or plain radiographic studies (listed in order of decreasing sensitivi ty). Plain radiographs may miss one-half or more cases but are useful in survey work. The main confounders are localised pleural thickenings caused by rib fractures, and subpleural fat; the latter sometimes requires CT scanning to differentiate. Except in certain restricted geographic localities, plaques signify temporally remote exposures to asbestos minerals. Plaques develop after rela tively low exposures and are thus not reliable indicators of elevated risk of asbestos-attributable lung fibrosis or lung cancer. Neither do they cause symp toms, or detectable reductions of the individual's lung function. In most set tings, plaques indicate an elevated risk of mesothelioma, in comparison to the general population. In comparison to similarly exposed persons, plaques do not have any prognostic significance.