PTGS2 and invasive ductal breast carcinoma: COX-2, cyclooxygenase-2; EPC, encapsulated papillary carcinoma; ER, estrogen receptor; HER2/neu, human epidermal growth factor receptor 2/neu protooncogene; IDC-NOS, infiltrating ductal carcinoma-not otherwise specified; ILC, invasive lobular carcinoma; IPC, invasive papillary carcinoma; PR, progesterone receptor