We identified an increased presence of phosphoproteins such as p-AKT1, p-STAT3, p-SMAD3, p-CREB1, p-p38, p-PTN11, and p-ERK1 in mammary tumors compared to the mammary gland, which should be further investigated as potential novel biomarkers in mammary carcinogenesis. This evidence concerns the gene SMAD3 and breast cancer.