PC-10 immunostaining of proliferating cell nuclear antigen in posterior uveal melanoma. Enucleation versus enucleation postirradiation groups.

PURPOSE: It is difficult to assess the viability of uveal melanoma after radiotherapy treatment. The purpose of the current study is to investigate PC-10 monoclonal antibody of proliferating cell nuclear antigen as a possible marker for cell proliferation and tumor viability in conventionally processed histologic preparations of uveal melanoma irradiated by brachytherapy as well as in nonirradiated melanomas.
METHODS: Thirteen enucleated eyes with posterior uveal melanoma that were treated by brachytherapy (cobalt 60 or ruthenium 106 radioactive plaques) were included in this study. Thirteen enucleated eyes of the same size with nonirradiated posterior uveal melanoma served as controls. The tumors were stained with PC-10 monoclonal antibody to proliferating cell nuclear antigen. All clinical and histologic data of the tumors were recorded and analyzed.
RESULTS: Five of the irradiated tumors showed positive staining with PC-10, although with a low score. Four of these tumors showed regrowth, and the fifth tumor was treated with a low-irradiation dose (5500 rad). In the nonirradiated tumor group, nine were positive for PC-10 staining, with a higher score. Significant correlation was found in this group between the PC-10 score and the mitotic figure count, but not with other prognostic factors. In three of four tumors that caused metastatic death, the PC-10 staining was positive and had a high score.
CONCLUSIONS: PC-10 immunostaining is a simple, reproducible method that can be applicable to conventionally processed histologic preparations. It clearly shows that cellular proliferation activity in nonirradiated and irradiated uveal melanomas. Based on the small number of cases reported herein, it seems that the PC-10 score can correlate with prognosis, but further studies should be performed.