Pleural Changes: Pleural thickening was more common in the cases with pleural plaques (35 patients) than in the controls (18 patients) and more severe (mean score of 0.74 vs 0.32; p<0.005).
Asbestos Bodies: Asbestos bodies were identified in routine histologic sections in eight of the cases with pleural plaques. In six of these cases, peribronchiolar fibrosis was also present (Fig 4). By definition, these six cases fulfill criteria for the diagnosis of asbestosis. The other pulmonary pathologic findings present in these six cases of asbestosis included pleural thickening (four cases), large scar (three cases), alveolar fibrosis (two cases), and one case each of interstitial fibrosis and scar-associated emphysema.
No asbestos bodies associated with peribronchiolar fibrosis were identified in the control group. Quantification of the total pulmonary burden of asbestos was not performed, and our data may therefore underestimate the number of cases of asbestosis.
Diseases caused by exposure to airborne asbestos fibers include pleural plaques, asbestosis, bronchogenic carcinoma, and mesothelioma.2 Pleural plaques, considered to be the hallmarks of exposure to asbestos, are smooth, raised white plaques which characteristically occur on the posterolateral aspect of the thorax and on the dome of the diaphragm. Pleural plaques are composed of relatively acellular hyalinized collagen. While pleural plaques are not diagnostic of exposure to asbestos, their presence is highly correlated with exposure to commercially used forms of asbestos. further
The clinical diagnosis of asbestosis, particularly mild forms of asbestosis, is fraught with difficulties. The changes in the chest roentgenogram include fine linear and irregular opacities in the lower pulmonary fields which progress to honeycombing of the lung; however, these findings are nondiagnostic, and a variety of other interstitial pulmonary diseases may give this same appearance. Nonetheless, medical and legal decisions are based on the interpretation of these radiographic abnormalities. It was hoped that CT and, in particular, HRCT would help resolve this dilemma and that the diagnosis of asbestosis could be firmly established by CT.
Figure 4. Diagnosis of asbestosis is based on association of asbestos bodies (arrowheads) with characteristic peribronchiolar fibrosis. A (upper), (hematoxylin-eosin, original magnification x 105); B (lower), (hematoxylin-eosin, original magnification X 600).