Primary epithelial tumour in the right atrium of the heart and inferior vena cava in NZR/gd inbred rats; pathology of 18 cases

Our plain-English summary of Primary epithelial tumour in the right atrium of the heart and inferior vena cava in NZR/gd inbred rats; pathology of 18 cases, by C.M. Goodall, G.S. Christie, J.V. Hurley (The Journal of Pathology, 1975).

The study

• Authors: C.M. Goodall, G.S. Christie, J.V. Hurley
• Journal: The Journal of Pathology
• Published: 1975;116(4):239-51
• Cited by: 25 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

In NZR/Gd inbred albino rats, tumours occurred in the right atrium or inferior vena cava of approximately 20 per cent. of untreated animals, of both sexes, over the age of 1 yr. The tumours were centred in the wall of the right atrium in 15 cases, and in the inferior vena cava in another three cases; they appeared to be primary in these sites. The tumours were slowly growing, but eventually malignant. Light- and electron-microscopic study showed the tumours were composed of epithelial alveoli imbedded in a collagenous connective tissue containing spindle cells and thin-walled blood capillaries. The epithelium varied from flat to low columnar, and often secreted mucoid material into the lumina, or sometimes into surrounding tissue. This tumour, for which the name atrio-caval epithelial mesothelioma is suggested, very closely resembles a rare epithelial tumour of the right atrium previously described in humans under a variety of names. An underlying embryological anomaly had been postulated in these tumours in humans, and the occurrence of pathologically similar lesions in high incidence in hearts of NZR/Gd inbred rats should help test the hypothesis of genetic and developmental causes in the genesis of this rare cardiac neoplasm.

In plain English

This was a pathology study in laboratory rats. It did not study asbestos or any other fiber exposure. The authors examined 149 untreated rats (66 male, 83 female) of an inbred albino strain, NZR/Gd, at the University of Otago, New Zealand. Fifty were killed in their first year, and 99 were kept until death or serious illness. Tumours were found in 18 rats: 15 in the wall of the heart's right atrium and 3, all males, in the inferior vena cava. The authors reported that these tumours occurred in approximately 20 per cent of animals aged 1 year or more, with no statistically significant difference between the sexes. Under light and electron microscopes, the tumours consisted of epithelial cells forming small cavities within fibrous tissue. They grew slowly but eventually became malignant. In one rat a metastasis was found in the wall of the pulmonary artery. The authors concluded that the tumours appeared to be primary where they were found. They suggested the name "atrio-caval epithelial mesothelioma" and said the tumours closely resemble a rare human right-atrial tumour. They noted that a genetic cause had not yet been proven.

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 pathology study (necropsy, light and electron microscopy) of spontaneous tumours in an inbred rat strain
• Who was studied: 149 untreated NZR/Gd inbred albino rats (66 male, 83 female) from the Department of Cancer Research, University of Otago, Dunedin, New Zealand. 50 were killed in their first year of life; the other 99 were kept until death or serious illness.
• Exposure: None. The rats were untreated, and the article does not concern asbestos or any other fiber exposure. The tumours arose spontaneously in this strain.
• Main results:
  • Of the 18 tumour-bearing rats, 15 had tumours in the right atrium of the heart.
  • Three male rats had tumours in the inferior vena cava, with the atrium free from tumour.
  • No statistically significant differences in tumour occurrence were found between sexes, or between virgins and breeders in either sex.
  • The first tumour was discovered at 428 days of age, when 128 rats were at risk.
  • Tumours spread in some rats: in four animals microscopic tumour emboli were found in pulmonary capillaries, and in one a metastasis was in the wall of the pulmonary artery.
  • The tumours grew slowly but were eventually malignant.
  • About one-quarter of tumour alveoli stained positive for mucus.
  • The authors found no evidence that the tumours arose from cardiac muscle, blood vessels or the cartilage of the atrioventricular plate.
• The authors' conclusion: The authors concluded that the tumours appeared to be primary in the right atrium or inferior vena cava. They suggested the name atrio-caval epithelial mesothelioma and said the tumour very closely resembles a rare epithelial right-atrial tumour described in humans. In their view, its high incidence in this strain supports the hypothesis that such tumours relate to errors of embryological development.
• Limitations the authors state:
  • The authors stated that a genetic cause in this strain had not yet been proven.

Topics

Medical terms in this study, explained in our Lexicon: Pathology, Alveoli, Spindle Cell, Epithelium, Mesothelioma, Neoplasm.

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