Establishment of Mammary Tumors by Injection of 7,12-Dimethylbenz[a]anthracene in Mammary Fat Pad of Rats

Chemical-induced mammary cancer models are widely used to mimic human breast carcinogenesis, with 7,12-dimethylbenz[a]anthracene (DMBA) being a commonly used agent. The oral administration of DMBA frequently results in the formation of tumors at random locations and carries significant risks, including high mortality rates and damage to various organs. To address these issues, this study employed a subcutaneous DMBA administration protocol to induce mammary cancer in rats. A total of twenty-four female Sprague-Dawley rats aged 45-55 days weighing 112-130 g were divided into four groups, including the control group injected with 0.75 mL corn oil (D0), a single dose of DMBA at 80 mg/kg BW (D1), two doses with a one-week interval (D2), and three doses with one-week intervals (D3), all administered via subcutaneous in mammary fat pad. Control groups (D0) did not show any tumor growth. Mammary tumor incidence increased with dosage (D1 33.33%, D2 66.67%, and D3 100%). Histopathological examination revealed the presence of various mammary tumor types without evidence of metastasis in all induced rats. All tumors originated from the injection site, and only a single nodule was observed in each rat. There were no significant differences in tumor grades between the treatment groups, and no mortality was recorded during the study. The D3 group showed the highest tumor incidence over the three-month observation period. These findings suggest that subcutaneous DMBA administration effectively induces mammary cancer in rat models with controlled tumor localization and minimal systemic effects, making it a promising method for experimental breast cancer studies.