PTGS2 and ductal breast carcinoma in situ: ,10 Comprehensive studies have identified several risk factors in DCIS, including high human epidermal growth factor 2 (HER2),11 p16 expression,10 cyclooxygenase-2 (COX-2) expression,11 periductal fibrosis11 and clinical and radiological factors such as young age,9,10 positive margins,9,10 mode of presentation10 and DCIS size.9