Hyperplastic Lesions in the Mammary Glands of Sprague-Dawley Rats After 7,12-Dimethylbenz[a]anthracene Treatment

Two groups of 50-day-old female Sprague-Dawley rats were given a single gavage of 7,12-dimethylbenz[a]anthracene dissolved in corn oil; a third group was untreated. The mammary gland wholemount preparations of tumor-bearing and tumor-free rats contained progressively greater numbers of hyperplastic lesions with increasing time after carcinogen treatment. The mammary glands of untreated rats remained free of these dyscrasias for the duration of the experiment. Several types of hyperplastic lesions were identified, but most were similar to the preneoplastic hyperplastic alveolar nodules in the mammary glands of some strains of mice. A relationship of these lesions to the histogenesis of carcinogen-induced mammary tumors of the rat is suggested but not yet established.