The purpose of our study was to evaluate the correlation between cyclooxygenase-2 (COX-2) and aromatase immunohistochemical expression in ductal carcinoma in situ (DCIS) and invasive ductal carcinoma (IDC) present in the same breast, as well as in adjacent stroma and normal epithelium, we still correlated with nuclear grade, histologic grade, presence or absence of comedonecrosis, tumor size, and age at diagnosis. Forty-seven cases were evaluated through the use of anti-aromatase and anti-COX-2 polyclonal antibodies. Making the correlation of COX-2 and aromatase expression, we observed that COX-2 expression in IDC was correlated with aromatase expression in IDC (p < 0.001), DCIS (p < 0.001), normal epithelium (p = 0.024), and stroma tumor (p < 0.001). When the correlation was made between COX-2 expression in DCIS with aromatase, we observed positive correlation in IDC (p < 0.001), DCIS (p < 0.001), normal epithelium (p = 0.013), and stroma tumor (p < 0.001). In the correlative analysis of COX-2 expression in normal epithelium with aromatase in different evaluated tissues, we observed the following statistical results: IDC (p < 0.001), DCIS (p < 0.001), normal epithelium (p = 0.005), and stroma tumor (p = 0.047). Our results demonstrate the high correlation between COX-2 and aromatase expression in IDC, DCIS and normal epithelium, showing the importance of these two enzymes in the induction, promotion and progression of breast cancer.