ERAS and breast cancer: We wondered about the biochemical changes caused in both normal and tumoral mammary glands by ERAS, and studied, in mammary glands on day 17.5 of pregnancy (in order to increase the relative amount of epithelial cells in the organ with respect to glands from virgin animals) and in K5-ERAS mammary tumors, the expression of genes related to proliferation, as Ccnd1, finding a significant increase in K5-ERAS tumors.