Hyperplastic and Inflammatory Nodules in the Canine Mammary

SUMMARY-Techniques developed for demonstrating hyperplastic lesions in mammary glands of rodents were applied to whole mammary glands of untreated female beagle dogs. Any unusual structural change, as com-pared to the normal lobularity of the mammary gland, was considered an atypical nodule. Such nodules were classified histologically as normal, inflammatory, or proliferative. Evaluation of the mammary gland of the dog by the techniques described could substantially shorten the time re-quired and improve the accuracy of oncologic and drug evaluation studies.-J Nat Cancer Inst 47:1277-1287,1971. IN MICE AND RATS, local hyperplasias exist which resemble the normal lobules of pregnancy, but occur in virgin or in nonpregnant, nonlactating, multiparous females. Certain of these localized areas recognized with dissecting microscope magni-fications were designated hyperplastic alveolar nodules and demonstrated to be preneoplastic (1, 2). The observation that a recognizable hyper-plastic lesion is the precursor of mammary tumor development in the mouse and the rat has prompted study of the dog to determine if similar lesions can be recognized in canine mammary glands. The techniques for the study of the rodent's mammary gland, although used to some extent in normal canine mammary gland studies (3), have not been applied to the investigation of canine mammary tumorigenesis and would seem to offer a means of scanning the entire mammary gland system for abnormalities. This study is an attempt to recognize by sub-gross morphology, with dissecting microscope magnifications, any abnormalities in the canine mammary glands and then to classify these struc-tures by histopathologic criteria