Asbestos Fiber Content of Lungs With Diffuse Interstitial Fibrosis: An Analytical Scanning Electron Microscopic Analysis of 249 Cases by ProQuest

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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.

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									                       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
roggl002@mc.duke.edu).                                 
								
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