PTGS2 and invasive ductal breast carcinoma: Association of expression of human epidermal growth factor receptor type 2 (HER-2) and cyclooxygenase-2 (COX-2) in non-neoplastic ducts, ductal carcinoma in situ (DCIS) and invasive ductal carcinoma (IDC) of the same breast and statistical analysis by the Spearman correlation (R)