Milky spots (Taches laiteuses) as structures which trap asbestos in mesothelial layers and their significance in the pathogenesis of mesothelial neoplasia

Our plain-English summary of Milky spots (Taches laiteuses) as structures which trap asbestos in mesothelial layers and their significance in the pathogenesis of mesothelial neoplasia, by K. Kanazawa, F.J. Roe, T. Yamamoto (International Journal of Cancer, 1979).

The study

• Authors: K. Kanazawa, F.J. Roe, T. Yamamoto
• Journal: International Journal of Cancer
• Published: 1979;23(6):858-65
• Cited by: 22 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

The UICC standard sample of asbestos, crocidolite, was injected subcutaneously into the flanks of CBA/lac mice. Asbestos fibres were found in milky spots in the serosal cavities more than 442 days after the injection, in the form of either naked fibres or asbestos bodies. Milky spots were the only structure in which asbestos fibres were observed in the mesothelial layer. The fact that asbestos fibres were found in the liver, spleen, kidney, brain, etc., in addition to milky spots, suggested that they were transported by the blood stream throughout the body. This assumption was confirmed by the similar distribution of asbestos after intravenous administration. The vascular and cellular structure of milky spots is such that they are particularly likely to trap blood-borne asbestos fibres. Hyperplastic changes were observed in milky spots after both subcutaneous and intravenous administration of asbestos in mice. The possible involvement of milky spots in the genesis of tumors of the mesothelium following exposure of animals to asbestos is discussed.

In plain English

This was an animal experiment in female CBA/lac mice. It looked at whether crocidolite asbestos reaches "milky spots", which are small clusters of blood vessels and cells in the linings of the chest and abdominal cavities. Forty mice received crocidolite under the skin of both flanks (60 mg in total), and 17 mice received 0.05 mg into a tail vein. Saline-treated mice served as controls. In the mice injected under the skin, no fibres were found in 32 mice examined before day 432. Of five mice killed between days 442 and 548, fibres were found in chest-cavity milky spots in three. Fibres also turned up occasionally in the liver, spleen, kidney and brain. In the intravenous group, all 12 mice killed at 160 and 167 days had enlarged milky spots, and fibres were seen in the milky spots of three of them. No mesotheliomas were seen in either group. The authors concluded that milky spots may trap blood-borne particles. They suggested that the cells' reaction to trapped fibres might be an early step toward tumours of the body cavities.

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: Animal experiment (mice given crocidolite under the skin or into a vein, with saline controls, and examined at various times after treatment)
• Who was studied: Female CBA/lac mice: 40 given asbestos under the skin and 20 saline controls; 17 given asbestos intravenously and 6 saline controls. A separate group of 10 mice was used to study the blood vessels of milky spots.
• Exposure: UICC standard crocidolite (medium-coarsely ground). Under the skin: 30 mg into each flank on two successive days (total 60 mg). Into the tail vein: a single dose of 0.05 mg.
• Main results:
  • Subcutaneous group: none of the 32 mice examined before day 432 showed asbestos fibres on routine examination.
  • Subcutaneous group: fibres (bare fibres or asbestos bodies) were first seen in chest-cavity (mediastinal) milky spots of a mouse killed at day 442. Of five mice killed from day 442 to day 548, fibres were found in three.
  • Subcutaneous group: fibres were occasionally seen in the liver, spleen, kidney and brain, but only a fairly long time after injection. None were seen in the intestinal walls, pelvic organs or chest wall.
  • Control mice did not show the milky-spot changes seen in treated mice, apart from a limited amount of haemosiderin (an iron pigment).
  • Intravenous group: five mice killed within 3 weeks showed no remarkable changes. All 12 mice killed at 160 and 167 days showed enlarged milky spots with more active scavenging (phagocytic) cells.
  • Intravenous group: fibres were identified in mediastinal milky spots in stained sections in 2 of the 12 mice. A further mouse showed fibres after microincineration (a method that burns away tissue to reveal mineral fibres).
  • Intravenous group: areas of overgrowth (hyperplastic foci) of the lining cells were seen in the parietal pleura in 6 of 12 animals.
  • No mesotheliomas or other tumours of the body cavities were seen in either the subcutaneous or the intravenous group.
• The authors' conclusion: The authors concluded that milky spots may serve to trap blood-borne particles as well as to clear material from the body cavities. They suggested that the reaction of the cells in milky spots to trapped asbestos fibres might be an early step in the development of tumours of the serosal cavity.
• Limitations the authors state:
  • The milky-spot-like structures in the parietal pleura along the ribs were not examined systematically. The authors noted that fibres might have been found in them with more extensive examination.

Topics

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

Medical terms in this study, explained in our Lexicon: UICC, Crocidolite, Asbestos Bodies, Mesothelium.

Related studies

• Black spots of the parietal pleura: morphology and formal pathogenesis — K.M. Müller, I. Schmitz, et al. (2002)
• Enhancement by asbestos of oncogenesis by Moloney murine sarcoma virus in CBA mice — K. Kanazawa, T. Yamamoto, et al. (1979)
• Histogenesis and fine structure of peritoneal tumors produced in animals by injections of asbestos — J.M. Davis (1974)
• Asbestos-activated peritoneal macrophages release a factor(s) which inhibits lymphocyte mitogenesis — K. Donaldson, J.M. Davis, et al. (1984)
• Pathogenesis of mesothelial reactions to asbestos fibers. Monocyte recruitment and macrophage activation — R.M. Branchaud, L.J. Garant, et al. (1993)
• Asbestos and neoplasia: diffuse mesothelial tumors. Criteria for diagnosis of diffuse mesothelial tumors — W.T. McCaughey (1965)

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