Mammary Neoplasia in the Female Rat After Neonatal and/or Adult 7,12-Dimethylbenz(a) Anthracene Administration

At 175 days of age it was found that DMBA given to female Sprague-Dawley rats at 2 days of age was followed by a high incidence of mammary fibroadenoma. DMBA given at 52 days of age was followed by a high incidence of mammary adenocarcinoma. When both DMBA treatments were given to the same animals, the mammary adenofibroma incidence was much the same as in the rats given only DMBA at 2 days of age and mammary adenocarcinoma incidence was much the same as in animals given only DMBA at 52 days of age. No significant interaction between two doses of DMBA given at both 2 and 52 days of age on mammary neoplasia was noted.