In this study, we evaluated COX-2 expression in DCIS using immunohistochemistry in comparison to expression in invasive cancer and normal breast, and investigated the association between COX-2 expression and cellular proliferation, nuclear grade and HER-2 antigen expression in DCIS, since HER-2 is overexpressed in at least two-thirds of in situ breast cancer (Allred et al, 1993; Bobrow et al, 1995; Suo et al, 2001). This evidence concerns the gene ERBB2 and ductal breast carcinoma in situ.