Mammary Adenocarcinoma

Malignant mammary tumors represent a relatively small percentage of mammary tumors in the laboratory rat. However, diagnostic pathologists in some laboratories have reported an increase in malignant mammary tumors in this species. Mammary adenocarcinomas have also been produced experimentally by estrogen administra­tion. A variety of patterns may be evident histologically. They have been classified by various terms, including “anaplastic adenocarcinoma” (Fig. 2.84), “cribriform,” “tubular," “papillary,” and “comedocarcinoma.”