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CONTEXT: Asbestosis is one of many forms of diffuse interstitial pulmonary fibrosis. Its histologic diagnosis rests on the pattern of fibrosis and the presence of asbestos bodies by light microscopy in lung biopsies. OBJECTIVE: To determine the asbestos fiber burden in patients with diffuse pulmonary fibrosis (DPF) who had a history of asbestos exposure, but whose biopsies did not meet established criteria for asbestosis, and compare it with the fiber burden in confirmed asbestosis cases. DESIGN: Fiber burden analysis was performed using scanning electron microscopy and energy-dispersive x-ray analysis of lung parenchyma from 86 patients with DPF and 163 patients with asbestosis. The correlation of the number of asbestos fibers found for a quantitative degree of fibrosis was analyzed. RESULTS: The fibrosis scores of the asbestosis cases correlated best with the number of uncoated commercial amphibole fibers. Seven DPF cases fell within the 95% interval of asbestos body count by light microscopy and 3 cases within that of the total commercial amphibole fiber count. CONCLUSIONS: Strict histologic criteria are useful for positive identification of asbestosis among cases of advanced pulmonary fibrosis. Few DPF patients with history of asbestos exposure whose biopsies did not meet the criteria for asbestosis may have asbestos fiber counts in the range seen in asbestosis, and fiber type identification by scanning electron microscopy with energy-dispersive x-ray analysis should be considered in these rare instances to avoid false-positive and false-negative diagnoses of asbestosis.
Asbestos Fiber Content of Lungs With Diffuse Interstitial Fibrosis An Analytical Scanning Electron Microscopic Analysis of 249 Cases Frank Schneider, MD; Thomas A. Sporn, MD; Victor L. Roggli, MD ● Context.—Asbestosis is one of many forms of diffuse in- related best with the number of uncoated commercial am- terstitial pulmonary ﬁbrosis. Its histologic diagnosis rests phibole ﬁbers. Seven DPF cases fell within the 95% inter- on the pattern of ﬁbrosis and the presence of asbestos bod- val of asbestos body count by light microscopy and 3 cases ies by light microscopy in lung biopsies. within that of the total commercial amphibole ﬁber count. Objective.—To determine the asbestos ﬁber burden in Conclusions.—Strict histologic criteria are useful for patients with diffuse pulmonary ﬁbrosis (DPF) who had a positive identiﬁcation of asbestosis among cases of ad- history of asbestos exposure, but whose biopsies did not vanced pulmonary ﬁbrosis. Few DPF patients with history meet established criteria for asbestosis, and compare it of asbestos exposure whose biopsies did not meet the cri- with the ﬁber burden in conﬁrmed asbestosis cases. teria for asbestosis may have asbestos ﬁber counts in the Design.—Fiber burden analysis was performed using scanning electron microscopy and energy-dispersive x-ray range seen in asbestosis, and ﬁber type identiﬁcation by analysis of lung parenchyma from 86 patients with DPF scanning electron microscopy with energy-dispersive and 163 patients with asbestosis. The correlation of the x-ray analysis should be considered in these rare instances number of asbestos ﬁbers found for a quantitative degree to avoid false-positive and false-negative diagnoses of as- of ﬁbrosis was analyzed. bestosis. Results.—The ﬁbrosis scores of the asbestosis cases cor- (Arch Pathol Lab Med. 2010;134:457–461) A sbestosis is a ﬁbrosing lung disease caused by expo- sure to asbestos. The degree of pulmonary ﬁbrosis is related to the ﬁber burden in the lung and the type and may be a surrogate marker for an individual’s exposure and has caused some degree of disagreement among ex- perts.2,3 Several studies have attempted to distinguish pa- duration of the exposure. The signiﬁcance of individual tients with background exposure from those whose ex- host factors remains uncertain. posure was at or above the threshold cumulative dose. Criteria for the histologic diagnosis of asbestosis have They found that 2 asbestos bodies per square centimeter been proposed by the Pneumoconiosis Committee of the correlated with a ﬁber burden 40 times that found in a College of American Pathologists (CAP) and the National reference population and that more than 95% of asbestosis Institute for Occupational Safety and Health (NIOSH).1 cases had more than 2 asbestos bodies per square centi- The CAP criteria require ‘‘discrete foci of ﬁbrosis in the meter.3,4 The 1997 Helsinki criteria incorporated these ﬁnd- walls of respiratory bronchioles associated with accumu- ings into more evidence-based criteria for the diagnosis of lations of asbestos bodies in histological sections.’’ The asbestosis, requiring (1) diffuse interstitial ﬁbrosis and (2) former criterion may be difﬁcult to assess in cases with 2 or more asbestos bodies within a section area of 1 cm2 diffuse ﬁbrosis and could overlap with other diseases or a count of uncoated asbestos ﬁbers that falls into the showing similar changes, for example, respiratory bron- range recorded by the same laboratory for asbestosis.5 chiolitis-associated interstitial lung disease or exposure to Histologic grading of asbestosis can be performed ac- various dusts other than asbestos. The latter criterion is cording to a NIOSH scheme that includes scores for both vague by not stating a minimal number of asbestos bodies severity and extent of disease.1 An expert panel convened required. The light microscopic count of asbestos bodies by the CAP is currently in the process of updating the asbestosis classiﬁcation scheme and diagnostic criteria, with results expected to be published in 2009. Accepted for publication May 22, 2009. From the Department of Pathology, Duke University Medical Center, Occasionally, one encounters diffuse pulmonary ﬁbrosis Durham, North Carolina. (DPF) in patients with a history of asbestos exposure, in The authors have no relevant ﬁnancial interest in the products or whom a diagnosis of asbestosis cannot be made due to companies described in this article. lack of the characteristic ﬁbrosis pattern or, more com- Presented in part at the Congress of the International Academy of monly, due to the lack of asbestos bodies in histologic sec- Pathology, Athens, Greece, October 16, 2008. Reprints: Victor L. Roggli, MD, Department of Pathology, Duke Uni- tions. Here we report the results of asbestos ﬁber analysis versity Medical Center, DUMC 3712, Durham, NC 27710 (e-mail: on 86 such cases. We determined the range of asbestos firstname.lastname@example.org).
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