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

Our plain-English summary of Comparative analysis of asbestos body and fiber content in formalin-fixed vs. paraffin-embedded lung tissue, by B.K. Kuhn, B. Vrugt, A. Low, et al (Frontiers in Public Health, 2025).

The study

• Authors: B.K. Kuhn, B. Vrugt, A. Low, J.E. Goodman, R. Attanoos
• Journal: Frontiers in Public Health
• Published: 2025;13:1590802
• Read it: PubMed · Publisher · Free full text

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.

Copyright © 2025 Kuhn, Vrugt, Low, Goodman and Attanoos.

In plain English

This study compared two ways of preparing the same lung tissue for asbestos counting: formalin-fixed 'wet' tissue and tissue recovered from paraffin wax blocks. It combined paired samples from 104 subjects. Sixty-two (75 sample pairs) were analyzed in Zurich, including 37 from an earlier study, and 42 post-mortem cases were analyzed in Cardiff. Both laboratories counted amphibole asbestos fibers; only Zurich counted asbestos bodies. Paraffin samples fell below the detection limit more often. In Zurich pairs that could be compared, paraffin counts tended to be lower. For asbestos bodies (54 pairs), a paired-difference test was not statistically significant (p = 0.06), while a second (Bland–Altman) analysis gave p = 0.047. For amphibole fibers (36 pairs), about 62% of paraffin samples were lower (p = 0.016). In Zurich, the difference would have changed the Helsinki-criteria classification for a twofold lung cancer risk in 6 of 54 cases using asbestos bodies and 7 of 36 using fibers. In Cardiff, the differences did not affect overall interpretation. The authors concluded that numeric fiber yields may vary between samples.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Comparative interlaboratory study of paired lung tissue samples from the same subjects, each prepared two ways (formalin-fixed versus paraffin-embedded), analyzed in a Swiss and a UK laboratory
• Who was studied: 104 subjects in total. Zurich: 62 patients (75 sample pairs, because 9 subjects had samples from several lobes), including 37 cases from an earlier study by Kuhn et al. and 25 new patients from the Silag archive (9 with asbestosis, 10 with mesothelioma, 6 with lung carcinoma). Cardiff: 42 subjects, post-mortem samples only. Study dates are not given.
• Exposure: Measured lung content of asbestos bodies (Zurich only) and amphibole asbestos fibers by transmission electron microscopy. Cardiff recorded grunerite, riebeckite, anthophyllite, tremolite, actinolite and chrysotile fibers. Zurich subjects had known, unknown or questionable asbestos exposure. Cardiff cases were submitted to investigate asbestos-related diseases in the absence of any known exposure.
• Main results:
  • Paraffin samples were more often below the limit of detection than formalin-fixed samples. In Zurich, asbestos bodies were below it in 18 paraffin samples (24%) versus 7 formalin-fixed (9%), and amphibole fibers in 35 paraffin (47%) versus 18 formalin-fixed (24%).
  • In Cardiff, amphibole asbestos fiber results were below the limit of detection in 35 paraffin samples and 12 formalin-fixed samples (of 42).
  • Zurich asbestos bodies (54 of 75 pairs above the detection limit): the paired differences between paraffin and formalin-fixed counts were not significantly different from zero (p = 0.06).
  • Zurich asbestos bodies: in the Bland–Altman analysis, the mean paired log10 difference between formalin-fixed and paraffin counts was 0.18 (p = 0.047), suggesting paraffin counts may tend to be lower. The linear regression slope was 0.77 (R2 = 0.64).
  • Zurich amphibole asbestos fibers (36 of 75 pairs evaluable): about 62% of paraffin samples had lower counts than the matching formalin-fixed samples. The difference was statistically significant (p = 0.016). The Bland–Altman mean log10 difference was 0.32, and the regression slope was 0.74 (R2 = 0.51).
  • Adding the Cardiff data (5 of 42 pairs evaluable) gave a Bland–Altman mean difference of 0.31 for amphibole fibers and a regression slope of 0.71 (R2 = 0.51).
  • In the Zurich data, the paraffin versus formalin-fixed difference would lead to a different Helsinki-criteria classification for a twofold lung cancer risk in 11% (6 of 54) of cases using asbestos bodies and 19% (7 of 36) using amphibole fibers. In Cardiff, the differences did not impact overall interpretation.
• The authors' conclusion: The authors concluded that numeric values for fiber yield may vary between samples prepared in different ways. In their discussion, they said the difference affects the conclusion about cause only in a small minority of cases.
• Limitations the authors state:
  • Paraffin samples contained varying amounts of paraffin, and asbestos bodies and fibers could be hidden under leftover paraffin debris.
  • Paraffin tissue samples were much smaller than formalin-fixed samples. Uneven distribution of asbestos in the lung may account for some of the differing results.
  • The study is subject to random error from how asbestos bodies and fibers are distributed across the lung.
  • Paraffin wax and water baths may be contaminated with asbestos fibers.
  • The relationship between the paired measurements was only moderate. A correction factor would give imprecise predictions, and each laboratory would need to establish its own regression.

Topics

Medical terms in this study, explained in our Lexicon: Asbestos Bodies, Fiber Burden, Mineral Fiber, Paraffin Block, Amphibole Asbestos, Respirable Fraction.

Related studies

• Discrepancies of asbestos body and fiber content between formalin-fixed and corresponding paraffin embedded lung tissue — B.K. Kuhn, F. Barresi, et al. (2021)
• Numerical and structural genomic aberrations are reliably detectable in tissue microarrays of formalin-fixed paraffin-embedded tumor samples by fluorescence in-situ hybridization — H. Horn, J. Bausinger, et al. (2014)
• Differential expression of N-cadherin in pleural mesotheliomas and E-cadherin in lung adenocarcinomas in formalin-fixed, paraffin-embedded tissues — A.C. Han, A. Peralta-Soler, et al. (1997)
• Validation of a Gene Expression Test for Mesothelioma Prognosis in Formalin-Fixed Paraffin-Embedded Tissues — A. De Rienzo, R.W. Cook, et al. (2017)
• Comparison of imaging based single-cell resolution spatial transcriptomics profiling platforms using formalin-fixed paraffin-embedded tumor samples — N. Ozirmak Lermi, M. Molina Ayala, et al. (2025)
• Comparison of imaging-based single-cell resolution spatial transcriptomics profiling platforms using formalin-fixed, paraffin-embedded tumor samples — N.O. Lermi, M.M. Ayala, et al. (2025)

Browse more research in Frontiers in Public Health, or return to medical research.