Black spots concentrate oncogenic asbestos fibers in the parietal pleura. Thoracoscopic and mineralogic study

Our plain-English summary of Black spots concentrate oncogenic asbestos fibers in the parietal pleura. Thoracoscopic and mineralogic study, by C. Boutin, P. Dumortier, F. Rey, et al (American Journal of Respiratory and Critical Care Medicine, 1996).

The study

• Authors: C. Boutin, P. Dumortier, F. Rey, J.R. Viallat, P. De Vuyst
• Journal: American Journal of Respiratory and Critical Care Medicine
• Published: 1996;153(1):444-9
• Cited by: 115 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Epidemiologic and pathologic data demonstrate that malignant mesothelioma occurs preferentially after exposure to long amphibole asbestos fibers. However, mineralogic studies have rarely detected such fibers in the parietal pleura. We hypothesized that the distribution of asbestos fibers in the pleura was heterogeneous and that they might concentrate in certain areas, as does coal dust in patients showing anthracotic "black spots" of the parietal pleura during thoracoscopy. We collected thoracoscopic biopsy samples from these black spots and from normal areas of the parietal pleura and lung from 14 subjects (eight with and six without asbestos exposure). Asbestos content was determined by transmission electron microscopy. In exposed subjects, mean fiber concentrations were 12.4 +/- 9.8 x 10(6) fibers/g of dry tissue in lung, 4.1 +/- 1.9 in black spots, and 0.5 +/- 0.2 in normal pleura. In unexposed patients, concentrations were 0, 0.3 +/- 0.1, and 0, respectively. Amphiboles outnumbered chrysotile in all samples. A total of 22.5% of fibers were > or = 5 microns in length in black spots. A histologic similarity of these black spots with milky spots is suggested by conventional and electron microscopy. We conclude that the distribution of asbestos fibers is heterogeneous in the parietal pleura. Indeed, the fibers concentrate in black spots, where they can reach high concentrations. These findings could explain why the parietal pleura is the target organ for mesothelioma and plaques.

In plain English

This thoracoscopic and laboratory study looked at whether asbestos fibers collect in "black spots." These are small coal-dust-stained areas sometimes seen on the parietal pleura, the lining of the chest wall. The authors took biopsies from black spots and from nearby normal-looking pleura in 14 consecutive patients, eight with and six without a history of asbestos exposure, and from the lung in 11 of them, and measured their asbestos fiber content. In exposed patients, mean concentrations were 12.4 million fibers per gram of dry tissue in lung, 4.1 million in black spots and 0.5 million in normal pleura. In unexposed patients they were 0, 0.3 million and 0. Normal pleura had significantly fewer fibers than lung or black spots. Amphiboles made up 95% of fibers in black spots, and 22.5% of black-spot fibers were 5 micrometers or longer. The authors concluded that fibers concentrate in black spots, which could explain why the parietal pleura is the target for mesothelioma and plaques. They noted the small number of patients studied.

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: Thoracoscopic and mineralogic study of a consecutive series of patients (case series), comparing fiber content in three sample types from each patient
• Who was studied: 14 patients undergoing thoracoscopy in whom anthracotic (coal-dust) black spots were seen on the parietal pleura: 8 with and 6 without a history of asbestos exposure. Pleural samples were taken from all 14. Lung samples were available for only 11 of them.
• Exposure: Asbestos exposure was occupational in six patients (jobs included insulation worker, shipyard worker, tunnel digger, mechanic), environmental in one patient who lived in Corsica, and both in one patient. Fibers found were mainly amphiboles (crocidolite, amosite, tremolite), with small amounts of chrysotile in some samples.
• Main results:
  • In asbestos-exposed patients, mean fiber concentrations (mean plus or minus SEM, per gram of dry tissue) were 12.4 ± 9.8 million in lung, 4.1 ± 1.9 million in black spots, and 0.5 ± 0.2 million in normal pleura.
  • In unexposed patients, concentrations were 0 in lung, 0.3 ± 0.1 million fibers per gram in black spots, and 0 in normal pleura.
  • Across all patients, the mean fiber concentration in normal-looking (nonanthracotic) pleura (0.3 ± 0.13 million per gram) was significantly lower than in lung or black spots (p less than 0.01).
  • Across all patients, mean concentrations in lung (7.9 ± 6.3 million per gram) and black spots (2.5 ± 3.7 million per gram) were not statistically different.
  • Amphibole fibers made up 99% of fibers in lung, 95% in black spots, and 61% in normal-looking pleura.
  • In black spots, 22.5% of fibers were 5 micrometers or longer and 10% were 8 micrometers or longer (lung: 21.7% and 11.4%). All fibers 5 micrometers or longer were amphiboles.
  • In the three patients with mesothelioma, asbestos burden was greater in black spots than in lung samples, but the difference was not significant.
  • Fibers in black spots were wider than lung fibers (mean diameter 0.19 versus 0.13 micrometers, p less than 0.001). Fiber length did not differ significantly.
• The authors' conclusion: The authors concluded that asbestos fibers are unevenly distributed in the parietal pleura and concentrate in black spots, where they can reach high concentrations. They wrote that this could explain why the parietal pleura is the target organ for mesothelioma and plaques.
• Limitations the authors state:
  • The difference in fiber burden between black spots and lung in mesothelioma patients was not significant, which the authors attributed probably to the small number of patients.
  • In one exposed patient with no fibers found in lung, inadequate lung sampling could not be ruled out.
  • The study was not designed to assess how fibers travel to the pleura.
  • Short, thin chrysotile fibers may have been harder to detect among the other particles in black-spot samples.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Asbestosis, Chrysotile, Mesothelioma.

Medical terms in this study, explained in our Lexicon: Parietal Pleura, Malignant Mesothelioma, Amphibole Asbestos, Pleura, Thoracoscopy, Thoracoscopic Biopsy, Asbestos Exposure, Transmission Electron Microscopy (TEM).

Related studies

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• Black spots of the parietal pleura: morphology and formal pathogenesis — K.M. Müller, I. Schmitz, et al. (2002)
• Chrysotile and tremolite asbestos fibres in the lungs and parietal pleura of Corsican goats — P. Dumortier, F. Rey, et al. (2002)
• Semi-Rigid Thoracoscopic Punch Biopsy Using a Hybrid Knife with a High-Pressure Water Jet for the Diagnosis of Pleural Effusions — Y. Yin, R. Eberhardt, et al. (2016)
• Environmental asbestotic pleural plaques in northeast Corsica: correlations with airborne and pleural mineralogic analysis — F. Rey, C. Boutin, et al. (1994)
• Asbestos, carbon nanotubes and the pleural mesothelium: a review of the hypothesis regarding the role of long fibre retention in the parietal pleura, inflammation and mesothelioma — K. Donaldson, F.A. Murphy, et al. (2010)

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