Structure and Composition of Pleural Plaques

Our plain-English summary of Structure and Composition of Pleural Plaques, by L. Le Bouffant, J.C. Martin, S. Durif, et al (1973).

The study

• Authors: L. Le Bouffant, J.C. Martin, S. Durif, H. Daniel
• Published: BIOLOGICAL EFFECTS OF ASBESTOS (J.C. WAGNER, EDITOR), LYON: IARC SCIENTIFIC PUBLICATIONS, VOLUME 8, PP. 249-257 (1973)
• Type of article: Conference paper
• Our copy: from Johns-Manville's own medical library. The article is still under copyright, so we describe it here rather than post it.

In plain English

This laboratory study examined pleural plaques from patients occupationally exposed to asbestos dusts, using microscopy and chemical analysis. For comparison, the authors examined a plaque from a person apparently not exposed to asbestos, a gas cyst and a tuberculous calcification. The plaques were collagen-rich tissue with few cells. Inflammatory-type cells were never found inside the plaque, though small clusters of such cells were seen at its edge. Most early calcium deposits gave diffraction patterns of whitlockite or apatite. However, the authors found significant differences in the deposits' phosphorus and calcium composition. The deposits closely resembled those in the comparison specimens. Hexosamines were higher in the calcified zone than in the fibrous zone. Very fine asbestos fibres, described as chrysotile, could be shown only after calcium and collagen were removed, and were more abundant in the calcified zone. The authors noted that fibrohyaline plaques are not specific to asbestos exposure. They concluded that fibrous tissue and calcification occurring together at this site suggests a definite relationship with the risk of asbestosis. Several pages are missing from the copy of the text used here.

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: Laboratory pathology study of human pleural plaque specimens (light microscopy, electron microscopy, electron diffraction, biochemical analysis), with comparison specimens of other origins
• Who was studied: Pleural plaques, taken preferably from the parietal pleura, from patients occupationally exposed to asbestos dusts. The surviving text does not state the number of patients; fibre counts are shown for two cases. For comparison, three specimens of calcifications of other origins were examined: a fibrohyaline plaque from a subject apparently not exposed to asbestos, a gas cyst, and a tuberculous calcification.
• Exposure: Occupational exposure to asbestos dusts. The fibres found in the plaques studied are described as chrysotile; the beginning of that sentence is missing from the text.
• Main results:
  • Inside the plaque, the tissue was fibrohyaline connective tissue, practically free of cells, and inflammatory-type cells were never found.
  • In the peripheral zone at the edge of the plaque, small clusters of lymphoplasmocytes, histiocytes or mast cells were seen near small vessels.
  • Most of the early (incipient) calcifications gave electron diffraction patterns corresponding to whitlockite (compact or lamellar ovoid forms) or apatite (needle-shaped, acicular crystals).
  • The authors described the calcifications as essentially of the whitlockite and apatite type. They found significant differences in the minerals' phosphorus and calcium composition, which they said needed more study.
  • Calcifications in the fibrous zone of parietal pleural plaques were similar to those in the thickened visceral pleura of the same individuals.
  • Calcifications in the three comparison specimens of different origin closely resembled those of pleural plaques.
  • There appeared to be no significant difference in collagen levels between the fibrous and calcified zones of calcified plaques.
  • Hexosamines were present in greater quantities in the calcified zone than in the fibrous zone.
  • Plaques from asbestos-exposed persons could contain considerable quantities of very fine fibres. These could be demonstrated only after the calcium deposits and collagen fibres were removed.
  • The fibres counted in the two cases had diameters of 25-30 nm. The fibre counts in Table 4 are not legible in the text.
  • The calcified zone contained more abundant fibres than the surrounding fibrous zones. The only plaques with massive calcifications contained large amounts of asbestos fibre.
  • The authors noted that fibrohyaline plaques are not the specific result of asbestos exposure and can be seen in other circumstances.
• The authors' conclusion: The authors noted that fibrohyaline tissue and calcification are each relatively common in general pathology. They concluded that the two occurring together at this site may be assumed to suggest a definite relationship with the risk of asbestosis.
• Limitations the authors state:
  • The authors stated that data on how plaques form were still very incomplete, so they could not outline the probable process of plaque formation.
  • The authors stated that a more thorough study was needed to clarify the differences in phosphorus and calcium composition of the minerals.

Topics

Medical terms in this study, explained in our Lexicon: Pleural Plaques, Collagen, Chrysotile, Asbestos Exposure.

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