BACKGROUND: Basic research using animal models is essential for investigating pathogenic molecular mechanisms and exploring new pharmaceutical treatments for tumors, including breast tumors. METHODS AND RESULTS: Thirty-six female Wistar rats, four weeks old, were included in the study, but six were excluded early due to health complications, leaving 30 rats in the final cohort. Mammary gland tumors were induced using a single subcutaneous dose of 20 mg 7,12-dimethylbenz(a)anthracene (DMBA) on the right side and MCF7 cells (xenograft) on the left thoracic gland. The experiment spanned 28 weeks. Blood and white cell counts were monitored at the start, mid-point, and end of the study. Tumorigenesis was achieved via both DMBA and MCF7 xenograft. Ovariectomy was performed on all rats, and tumors became palpable after the fifth week following DMBA and MCF7 administration. CONCLUSIONS: Oncogenesis using DMBA and MCF7 xenograft simultaneously had not been previously attempted. The results showed a 16.7% (6/36) animal mortality rate in the early stages of experimentation and a 100% induction of palpable tumors in the surviving animals.