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Comparative Study
. 2025 Jun 11:13:1590802.
doi: 10.3389/fpubh.2025.1590802. eCollection 2025.

Comparative analysis of asbestos body and fiber content in formalin-fixed vs. paraffin-embedded lung tissue

Barbara K Kuhn  1 , Bart Vrugt  1   2 , Alex Low  3 , Julie E Goodman  3 , Richard Attanoos  4
Affiliations
Comparative Study

Comparative analysis of asbestos body and fiber content in formalin-fixed vs. paraffin-embedded lung tissue

Barbara K Kuhn et al. Front Public Health. .

Abstract

Introduction: Asbestos body and fiber burdens may be determined using different preparations of lung tissue. Paraffin-embedded tissue requires more complex steps than formalin-fixed tissue. A prior study highlighted potential variations in the measurement of retained mineral fibers in different lung preparations and prompted this expanded interlaboratory analysis. Data from exposed subjects referred to a Swiss laboratory were compared with the results of mineral analysis obtained from a laboratory based in the United Kingdom.

Methods: Numbers of asbestos bodies were determined in formalin-fixed tissue and corresponding paraffin blocks of 62 subjects in Zurich by NaOCl digestion. Fiber burden was measured in a total of 104 subjects (62 subjects in Zurich and 42 subjects in Cardiff).

Results: Asbestos body and amphibole asbestos fiber counts obtained from paraffin blocks were noted to be, in general, lower than counts obtained from formalin-fixed tissue. The limits of detection were higher in paraffin blocks than in formalin-fixed tissue. Similar trends were obtained in the two laboratories.

Discussion: In this comparative mineral analytic study, the authors focused on the potential significance of differing specimen preparations (formalin-fixed wet lung versus paraffin wax-embedded block extraction) investigating paired samples. The results generally reflect numerically higher fiber burdens in samples analyzed from wet lungs compared with counterpart paraffin wax tissue. Mineral analysis by electron microscopic analysis remains the most objective measure of the respirable fraction of mineral dust as it correlates most directly with disease risk.

Keywords: amphibole asbestos fibers; asbestos bodies; formalin-fixed lung tissue; paraffin block; paraffin-embedded tissue.

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Conflict of interest statement

JG serves as a member of the National Stone, Sand and Gravel Association (NSSGA) Scientific Advisory Board. She has provided expert testimony in asbestos litigation and has engaged in scientific consultation with both public and private entities, including NSSGA. RA has provided expert testimony in medicolegal cases for claimants, defendants and on joint basis. In addition, RA is appointed by the Court as an independent expert in suspected asbestos disease deaths. RA is a member of the National Stone Sand and Gravel Association Scientific Advisory Board. He receives no stipend for this work and has received no funding for this work. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Figures

Figure 1
Figure 1
Comparison of asbestos body (AB) counts in formalin-fixed (FF) lung tissues and paraffin-embedded (PE) lung tissue of the same patients. According to the Helsinki criteria, 1,000 AB/g dry LT (purple dashed line) indicates a high probability of exposure to asbestos dust, and 5,000 AB/g dry LT (red solid line) is related to a 2-fold risk of developing lung cancer. The blue dotted line is the line of equality, the yellow solid line is the linear regression fit of log10 transformed residuals, and the dashed yellow lines are the 95% confidence interval of the regression.
Figure 2
Figure 2
Bland–Altman plot showing the mean difference between asbestos body (AB) counts in formalin-fixed (FF) lung tissue and paraffin-embedded (PE) tissue and the 95% limits of agreement (dashed blue line). Counts are logarithmically transformed to meet assumptions of normality.
Figure 3
Figure 3
Amphibole asbestos fiber (AAF) counts in formalin-fixed (FF) lung tissue and paraffin blocks (PE) of the same patients. According to the Helsinki criteria, 1 Mio amphibole fibers (>1 μm)/g dry LT (purple dashed line) indicate a high probability of exposure to asbestos dust, and 5 Mio amphibole fibers (>1 μm)/g dry LT (red solid line) are related to a 2-fold risk of developing lung cancer. The blue dotted line is the line of equality, the yellow solid line is the linear regression fit of log10 transformed residuals, and the dashed yellow lines are the 95% confidence interval of the regression.
Figure 4
Figure 4
Bland–Altman plot showing the mean difference between amphibole asbestos fiber (AAF) counts in formalin-fixed (FF) lung tissue and paraffin-embedded (PE) tissue and the 95% limits of agreement (dashed blue line). Counts are logarithmically transformed to meet assumptions of normality.
Figure 5
Figure 5
Combined data Zurich (black) and Cardiff (blue). Amphibole asbestos fiber (AAF) counts in formalin-fixed (FF) lung tissue and paraffin blocks (PE) of the same patients. According to the Helsinki criteria, 1 Mio amphibole fibers (>1 μm)/g dry LT (purple dashed line) indicate a high probability of exposure to asbestos dust, and 5 Mio amphibole fibers (>1 μm)/g dry LT (red solid line) are related to a 2-fold risk of developing lung cancer. The blue dotted line is the line of equality, the yellow solid line is the linear regression fit of log10 transformed residuals, and the dashed yellow lines are the 95% confidence interval of the regression.
Figure 6
Figure 6
Combined data Zurich (gray) and Cardiff (blue). Bland–Altman plot showing the mean difference between amphibole asbestos fiber (AAF) counts in formalin-fixed (FF) lung tissue and paraffin-embedded (PE) tissue and the 95% limits of agreement (dashed blue line). Counts are logarithmically transformed to meet assumptions of normality.
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