Asbestosis, pleural plaques and diffuse pleural thickening: three distinct benign responses to asbestos exposure

Abstract

The aim of this study was to investigate by computed tomography (CT) whether asbestosis, diffuse pleural thickening and/or pleural plaques are statistically associated. We also tried to find criteria to differentiate between diffuse and circumscribed pleural thickening. From 231 exposed workers, only those subjects whose radiograph showed neither bilateral calcified pleural plaques nor small pulmonary opacities higher than 1/1 grade according to the 1980 International Labour Office (ILO) Classification were considered. Scans were assessed for the presence of subpleural curvilinear lines, septal and intralobular lines, parenchymal bands, honeycombing, rounded atelectasis, pleural plaques and diffuse pleural thickening. CT scans revealed pleural and/or lung abnormalities in 99 workers. Pleural plaques were unilateral in one-third of cases with plaques. Diffuse pleural thickening, parenchymal bands and rounded atelectasis were unilateral in, respectively, 62 and 69 and 75% of cases with the abnormality. Septal and intralobular lines, and honeycombing were always bilateral. CT signs could be grouped into three patterns: 1) septal and intralobular lines, and honeycombing corresponding to pulmonary fibrosis; 2) pleural plaques corresponding to parietal pleural fibrosis; and 3) diffuse pleural thickening, rounded atelectasis and parenchymal bands corresponding to visceral pleural fibrosis. In these workers with a normal or near-normal radiograph, three groups of subjects with different responses were distinguished. Crow's feet and rounded atelectasis help to differentiate plaques from diffuse thickening.

Are pleural plaques an appropriate endpoint for risk analyses?

“…Care must be taken to distinguish pleural plaques from other pleural abnormalities, such as diffuse pleural thickening [DPT] (Copley et al, 2001;Gevenois et al, 1998;Jeebun & Stenton, 2012;McLoud et al, 1985;Miles et al, 2008) or asbestosis, which have substantially different biological effects.…”

Interobserver Variations in Diagnosing Asbestosis According to the ILO Classification

“…In a study which included 551 chest radiographs reinterpreted by six independent consultants in chest radiology, Gitlin et al (14) concluded that the difference between interpretations by initial readers and reinterpretations was too great to be attributed to interobserver variability. It has to be stressed, however, that in most cases the reinterpretations of small opacity profusions were more accurate than those reported by initial readers (14)(15)(16)(17).…”

“…High-resolution computed tomography (HRCT) has proved to be a simple, reliable, and reproducible method for classifying lung fi brosis and diagnosing asbestosis, and it would be possible to use it as a part of an international classifi cation (11,12). Gamsu found that high-resolution CT scans had a higher detection rate for interstitial fi brosis than chest radiographs classified according to the ILO classification in occupationally exposed population (6).…”

Endoscopic diagnosis and management of pleural effusion in malignant pleural mesothelioma

“…The presence of fibrohyaline plaques (areas of hard whitish fibrous tissue, with well-defined borders, sometimes with pearl-like nodules) ( Figure 4) indicates a previous asbestos exposure, and is often associated with MPM (23,24).…”

“…The second priority is a good knowledge of the macroscopic normal appearance of the pleura and of its pathological processes, in order to clearly identify inflammatory or neoplastic lesions, irrespective of their origin (23,24).…”