Abstract
In a previous communication 1 the histological changes produced in the mammary gland of the rabbit by the inversion of nipple flaps were reported. Various proliferative changes in the inverted skin and glandular epithelium occasioned by the procedure were described. The defensive factors of the rabbit host to the continued growth of the stimulated and proliferating epithelium were noteworthy. Most of the nodules thus produced were eventually fibrosed or absorbed. Certain of the larger nodules, persisting now far more than a year, have been found to contain altered skin and its appendages which produce retention cystic masses.
As tumors of the mammary gland of the rabbit rarely occur it was concluded that even though the normal glandular epithelial cell
relationships had been greatly disturbed and the epithelium provoked to considerable proliferation, the lack of susceptibility of the animal to such tumor growths or rather it capable defensive barriers prevented the continued growth.
For these reasons it was considered that some other animal of sufficient size and known to be susceptible to epithelial neoplasia of the mammary gland would be preferable. The literature shows that dogs are victims of mammary carcinonia. In 603 cases compiled by Steeker 2 299 (49.5 per cent) were mammary carcinoma. In 50 of these, where the age was known, 23 occurred between the ages of 7 and 10 years. Feldman 3 studied 132 tumors from various animals among which 17 were from dogs. Of these 17 only 3 were carcinoma, the location of which are not mentioned. Although the incidence of occurrence of mammary carcinoma in the dog is difficult to ascertain, nevertheless such an animal is at times a victim to cancerous growth of the breast.
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