Cyclooxygenase 2 expression in pterygium

PURPOSE: Following the recent discovery of an abnormal expression of the p53 gene in the epithelium in pterygium, some researchers felt that pterygium is a tumor rather than a degenerative disease. Ultraviolet (UV) radiation has been reported to be associated with pterygium formation, however the mechanism whereby UV induces uncontrolled proliferation in pterygial cells is unclear. Because cyclooxygenase 2 (COX 2) was reported to exist and play an important role in UV-related cutaneous carcinogenesis, it is logical to suspect that COX 2 existed in pterygium. This study was designed to investigate the expression of COX 2 in pterygium. METHODS: Immunohistochemical staining using a monoclonal antibody to COX 2 was performed on 90 pterygial specimens, 40 normal conjunctiva, and 5 normal limbus. RESULTS: In the pterygium group, 75 (83.3%) specimens stained positive for COX 2. The staining was limited to the cytoplasm of the epithelial layer and predominantly over the basal epithelial layer. No substantial staining was visible in the subepithelial fibrovascular layers. All specimens were negative in the normal conjunctiva and limbus group. CONCLUSIONS: The present study showed COX 2 existed in pterygium. Given the role of COX 2 in cutaneous tumor carcinogenesis, we suggest COX 2 may also play a role in pterygium formation. This study could be used as the basis for future surveys of the causal relationship between COX 2 and pterygium as well as the effect of COX 2 inhibitor in preventing primary or recurrent pterygium.