Smoking-associated fibrosis and pulmonary asbestosis

The diagnosis of pulmonary asbestosis is most often established based on clinical criteria and has both clinical and legal implications. Unfortunately, one of the confounding features in the diagnosis may be a history of cigarette abuse, which can produce interstitial opacities on chest imaging as well as diffusion defects on pulmonary function testing, criteria that are used in the diagnosis of pulmonary asbestosis. The objective of the present study was to evaluate the correlation of radiographically detected pulmonary fibrosis with fibrosis established histopathologically as attributable to asbestos, in a cohort referred for diagnosis of an asbestos-related malignancy in the context of litigation. We examined the slides of 186 cases with reported asbestos exposure, referred in consultation for asbestos-related malignancy and the presence of pulmonary fibrosis. Sixty-five cases had what was judged to be adequate tissue sampling for histopathologic evaluation of asbestosis as well as an existing radiologic assessment of pulmonary fibrosis by B-reader report. Of 24 cases judged to have asbestosis radiographically, which had sufficient tissue for pathologic examination, six showed asbestosis histopathologically. The remaining 18 cases (mean smoking history of 53 pack-years) showed interstitial fibrosis that was judged to be most consistent with smoking-associated pulmonary fibrosis. We conclude that the clinical diagnosis of mild asbestosis cannot be reliably distinguished from interstitial fibrosis in heavy smokers.