Cyclooxygenase-2 expression in borderline ovarian tumors

The aim of the study was to investigate by immunohistochemistry the expression of cyclooxygenase-2 (COX-2) in a single institutional series of borderline ovarian tumors (BOT). Moreover, to perform a comparative analysis, COX-2 expression was also analyzed in benign and malignant ovarian tumors.

Paraffin-embedded sections form 51 BOT, 26 benign, and 37 malignant ovarian tumors were incubated with polyclonal antiserum against COX-2. The results were calculated as the product of the percentage of the immunostained tumor cells by the relative staining score. Cases with immunostaining values of >1 were considered COX-2-positive.

Thirty-four (66.7%) of fifty-one BOT were considered as COX-2-positive, and this rate was not significantly different with respect to COX-2 positivity in benign (50.0%) and in malignant (51.3%) ovarian tumors (P value = 0.23). A significantly higher percentage of COX-2 positivity was found in serous (24 of 24, 100%) with respect to mucinous (9 of 26, 34.6%) BOT (P value = 0.0001). Moreover, 7 (63.6%) of 11 endocervical-type mucinous borderline ovarian tumors were COX-2-positive with respect to only 2 of 15 (13.3%) intestinal-type mucinous BOT (P value = 0.013). The same trend was observed in benign lesions, with COX-2 positivity in 9 of 11 (81.8%) of serous versus 4 of 15 (26.7%) of mucinous tumors (P value = 0.015). On the other hand, no difference was found in the percentage of COX-2 positivity in serous (14 of 29, 48.3%) versus mucinous (5 of 8, 62.5%) ovarian carcinomas (P value = 0.22).

COX-2 is differently expressed in BOT according to different histotype. Moreover, an increase of COX-2 positivity was observed from mucinous intestinal BOT to frankly malignant ovarian tumors suggesting that COX-2 overexpression might be involved in mucinous ovarian carcinogenesis.