Background: Transitional Cell Carcinoma (TCC) is the most common type of urinary bladder cancer. Cyclooxygenase-2 (COX-2), a key enzyme in prostaglandins biosynthesis, has been introduced as a new candidate for targeted therapy in this cancer. In this study, we investigated the expression of COX-2 in urinary bladder TCCs and its relationship with clinicopathological parameters such as tumor grade and stage.

Methods: This cross-sectional study was performed in the Pathology department of Sina Hospital in Tehran, Iran during 2006-2011. Pathology reports of patients with definite diagnosis of urinary bladder TCCs who had undergone Transurethral Resection (TUR) were reviewed and 40 cases were selected. Subsequently, COX-2 expression was assessed immunohistochemically by the examination of paraffin embedded tissue blocks. Staining in more than 5% of tumor cells was considered as positive expression.

Results: COX-2 was expressed in 52.5% of the patients. High-grade tumors revealed a higher (87.5%) COX-2 expression versus other grades of the lesions and there was a statistically significant difference in COX-2 expression between them (P<0.001). Patients' age was also related to the expression of this marker (P=0.03). In contrast, this marker did not correlate with other characteristics including gender, lymphatic invasion or tumor stage. In addition, perineurial or vascular invasions were not detected in any of the patients.

Conclusion: COX-2 expression was seen in more than half of our patients and it had a marked relation to tumor differentiation. Accordingly, this molecule may be a useful tumor marker in the assessment of urinary bladder cancers.