COX-2 expression in lobular in situ neoplasia of the breast: correlation with histopathological grading system according to the Tavassoli classification

Aims: There is considerable evidence to link cyclo-oxygenase (COX)-2 to the development of cancer. The aim of this study was to assess COX-2 expression and its subcellular localization in lobular in situ neoplasia (LIN) of the breast and to verify differences in COX-2 expression between different grades of lesions according to the Tavassoli classification. Methods and results: We analysed the expression of COX-2 protein by immunohistochemistry in tissue samples of 51 LIN lesions classified into three grades according to the Tavassoli classification. COX-2 immunostaining was observed in 78.4% of LIN samples and showed a prevalent membranous rather than cytoplasmic pattern. COX-2 was expressed in 16/17 (94.1%) LIN1, 22/25 (88%) LIN2 and 2/9 (22.2%) LIN3. As regards COX-2 expression, a statistically significant difference was found between LIN1 and LIN3 (P = 0.001) and between LIN2 and LIN3 (P = 0.001). No difference was found between LIN1 and LIN2. Moreover, a significant negative correlation was found between LIN grade and COX-2 expression (P < 0.0001). Conclusions: COX-2 is highly expressed in LIN, supporting a role for this protein in the early stage of breast carcinogenesis, representing the rationale for using COX-2 selective inhibitors in the earliest stages of breast cancer.