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MC Mendez, L Fernandes, AL Caissie, SA Callejo, MN Burnier; Cyclooxygenase-2 (COX-2) Expression In Retinoblastoma . Invest. Ophthalmol. Vis. Sci. 2002;43(13):2582.
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Purpose: Retinoblastoma (RB) is the most common ocular tumor in children. Histopathologicaly, it is characterized by a sleeve pattern particularly when the tumor is vascularized by the retinal vessels. However, when the tumor invades the choroid and optic nerve (O.N), there is a change in the vasculature source and the neoplastic cells acquire a diffuse pattern. COX-2 is a prostaglandin synthetase involved in many processes such as angiogenesis, tumor invasion, and metastasis. The objective of this study is to determine the expression of COX-2 and its possible role in the vascularization of RB. Methods: Sixteen formalin-fixed paraffin-embedded specimens of RB were collected from The Henry C. Witelson Eye Pathology Laboratory at McGill University. Immunohistochemical staining was performed in all cases using a monoclonal antibody against COX-2. Slides were reviewed to determine the degree of differentiation, the presence of choroidal and O.N invasion as well as the pattern of COX-2 expression. Results: Six of the 16 RB were considered to be well-differentiated tumors, six were poorly differentiated, and the remaining four were of an intermediate degree of differentiation. Two of the 16 tumors showed only O.N invasion, four had choroidal invasion only, and five tumors presented with simultaneous choroidal and O.N invasion. In all cases the expression of COX-2 was completely negative in the bulk of the tumor regardless of the degree of differentiation. Four out of the seven cases, with O.N invasion were positive for COX-2 in the tumor cells infiltrating up to and through the lamina cribosa. The other three cases with more extensive invasion of the O.N were found to be COX-2 negative. The area of the choroidal invasion was negative in all cases. Conclusion: The expression of COX-2 in RB may play an important role in the early stages of the O.N invasion however COX-2 expression is lost as the tumor cells extend beyond the lamina cribosa. The acquired COX-2 expression of the invading cells could be explained by a change of the angiogenic pattern of the tumor and/or changes of the invasive properties of those RB cells.
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