Histogenesis and fine structure of peritoneal tumors produced in animals by injections of asbestos

Our plain-English summary of Histogenesis and fine structure of peritoneal tumors produced in animals by injections of asbestos, by J.M. Davis (Journal of the National Cancer Institute, 1974).

The study

• Author: J.M. Davis
• Journal: Journal of the National Cancer Institute
• Published: 1974;52(6):1823-37
• Cited by: 55 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Primary tumors of the peritoneal cavity were produced in rats and mice by the intraperitoneal injection of crocidolite asbestos. The earliest discernible neoplastic stage consisted of many small, pedunculated nodules scattered over the surfaces of the viscera, diaphragm, and body wall. These nodules contained a central core of reticulin or collagen surrounded by layers of pleomorphic connective-tissue cells. The surfaces of the nodules were covered by a single layer of epithelial cells similar to normal mesothelium. In later stages some nodules remained distinct and became quite large, but often the tumor spread over the peritoneal surfaces as a uniform sheet. The cells found in sheets were mostly of the same type as those in large nodules: pleomorphic connective-tissue cells in the central regions and epithelial cells on the surface. In some advanced tumors, however, the cells had a spindle-cell pattern similar to a fibroma or fibrosarcoma. In this form the neoplasms were locally invasive; however, at earlier stages no signs of invasion could be detected. Electron microscope studies showed only a slight difference in ultrastructure between the different tumor cell types, and it is suggested that the growths arose from undifferentiated mesenchymal cells in the submesothelial tissues. These cells retained their normal pleomorphic pattern or gave rise to either epithelial (mesothelial) cells on free surfaces or spindle cells in deeper layers.

PubMed has no abstract for this study. This is the authors' abstract, copied from the article.

In plain English

In this animal experiment, the author injected asbestos dust into guinea pigs, rats and mice and examined the tissue under light and electron microscopes. After chrysotile or crocidolite was injected into the chest (pleural) cavity of 100 guinea pigs and 150 mice, only 1 pleural tumor was found in the guinea pigs and 2 in the mice, all in animals given crocidolite. After crocidolite was injected into the abdominal (peritoneal) cavity of 25 rats and 60 mice, tumors were reported as 17 in rats and 20 in mice. Some of these animals were killed at intervals to study early stages. The first tumors appeared around 9 months after injection as small nodules on the abdominal organs. The single layer of mesothelial cells lining the cavity never showed hyperplasia (overgrowth). Tumors invaded nearby tissue only when their cells took a spindle shape, and the different tumor cell types differed little in fine structure. The author concluded that the tumors appeared to arise not from the mesothelial lining but from connective tissue cells just below it.

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: injection of asbestos into the pleural or peritoneal cavity, with light and electron microscope study of the resulting tumors
• Who was studied: Guinea pigs (Duncan Hartley), rats (Wistar) and mice (BALB/c). The pleural injection series used 100 guinea pigs and 150 mice. The peritoneal injection series used 25 rats and 60 mice. Work was done at the Institute of Occupational Medicine, Edinburgh, Scotland; dates of the experiments are not given.
• Exposure: Two samples of chrysotile and two of crocidolite: Reading University samples and UICC standard reference samples. Guinea pigs and rats received 25 mg of dust in 1 ml distilled water; mice received 10 mg in 0.5 ml. Pleural injections used chrysotile or crocidolite. Peritoneal injections used UICC crocidolite only.
• Main results:
  • After pleural injection, 1 pleural tumor was found in 100 guinea pigs and 2 in 150 mice
  • All of these pleural tumors were in animals given crocidolite
  • Guinea pigs and mice appeared extremely resistant to tumor induction in the pleural cavity
  • After intraperitoneal injection of crocidolite, tumors were reported as 17 in rats (25 injected) and 20 in mice (60 injected). Some animals in this series were killed at intervals.
  • The first peritoneal tumors were found in both rats and mice around 9 months after dust injection
  • The earliest signs of tumor formation were numerous small nodules scattered over the mesentery and omentum
  • The single layer of mesothelial cells did not show hyperplasia at any stage of tumor induction
  • Invasion of nearby tissue was found only where tumor cells had a spindle-cell pattern
  • When tumor cells took on the spindle-cell form, this change was not at first accompanied by marked changes in their fine structure under the electron microscope
  • All animals with advanced tumors developed ascites (fluid) in the peritoneal cavity
• The authors' conclusion: The author concluded that the site of tumor origin did not appear to be the mesothelial cell lining of the peritoneal cavity, but connective tissue cells just below the mesothelium
• Limitations the authors state:
  • The pleural tumors were not found until well advanced, so their sites of origin could not be detected
  • It is extremely difficult to detect the exact point at which neoplastic change occurs in an area of previous inflammation
  • Pleural injections in rats and peritoneal injections in guinea pigs had not yet been done

Topics

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

Medical terms in this study, explained in our Lexicon: Peritoneal Cavity, Crocidolite, Diaphragm, Collagen, Pleomorphic, Mesothelium, Neoplasm, Spindle Cell.

Related studies

• Epithelial outgrowths from lung tissue following intrapleural injection of asbestos dust in experimental animals — J.M. Davis (1971)
• The calcification of fibrous pleural lesions produced in guinea-pigs by the injection of chrysotile asbestos dust — J.M. Davis (1971)
• The fine structure of so-called minute pulmonary chemodectomas — C. Kuhn, F.B. Askin (1975)
• The histopathology and ultrastructure of pleural mesotheliomas produced in the rat by injections of crocidolite asbestos — J.M. Davis (1979)
• Characteristics of peritoneal macrophages induced by asbestos injection — K. Donaldson, J.M. Davis, et al. (1982)
• Acute and chronic effects of intraperitoneal injection of two types of asbestos in rats with a study of the histopathogenesis and ultrastructure of resulting mesotheliomas — M.L. Shin, H.I. Firminger (1973)

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