Purpose: To provide insight into the relationship between cyclooxygenase-2 (COX-2) expression and histopathologic features of retinoblastoma specimens treated either by primary or secondary enucleation. Design: Laboratory investigation. Methods: Twenty-five retinoblastoma specimens received between 1994 and 2003 were retrieved for this study from the Ocular Pathology Registry, Federal University of São Paulo, Brazil and the Henry C. Witelson Ocular Pathology Laboratory and Registry, McGill University, Montreal, Canada. The specimens retrieved were divided into two groups: Group I, enucleation was performed as a form of primary treatment (n = 15) and Group II, enucleation after failure of conservative treatment (n = 10). Patient information and formalin-fixed, paraffin-embedded specimens were obtained. New sections of these blocks were used for hematoxylin and eosin stain and for immunoassay using a monoclonal mouse anti-COX-2 antibody. Two independent ophthalmic pathologists reviewed all of the microslides. Results: Twenty-three specimens (92%) presented a high expression of COX-2 (15 in Group I; eight in Group II) and there was no statistical difference in COX-2 expression between the two groups (P = .07). However, all specimens expressed COX-2 to a different degree. The areas of tumor invasion were positive for COX-2 in 87.5% of the two groups. Conclusion: Most retinoblastoma specimens revealed a high COX-2 expression. Future studies will be necessary to correlate the high expression of COX-2 in retinoblastoma and a possible applicability of anti-COX-2 medications in the treatment of these tumors.
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