Expression of c-Kit and its ligand SCF in primary uveal melanoma

Purpose. To evaluate the concurrent rate of expression of c-Kit and its ligand stem cell factor (SCF) in uveal melanoma in respect to the further clinical course and the correlation of these markers. Methods. Paraffin sections from 35 primary uveal melanomas were evaluated immunohistochemically for the expression of c-Kit and SCF. Sixteen cases developed systemic metastasis during the followup (median: 5 years after diagnosis). The patients who did not develop metastasis (n=19) had a mean follow-up of 10.6 (9-13) years. Radiation was performed in 6 patients. Results. c-Kit and SCF were expressed in all patients who did or did not develop metastasis in the further clinical course. A mean SCF expression of 77.2% (range 52.7%-97.5%) of tumors that did not develop systemic metastasis and 30.1% (range 2.9%-61.5%) of tumors with systemic metastasis were evident. Uveal melanomas revealing an increased SCF expression were found to develop no metastasis more frequently (p<0.0001; hazard ratio (HR)=0.963, 95% confidence interval (CI) 0.945-0.981). A mean c-Kit expression of 58.01% (range 5.9%-97.9%) in the group who did not develop metastasis and 48.9% (range 5.0%-95.9%) in the group with systemic metastasis were observed. c-Kit expression was not associated with increased rates of metastasis formation (p=0.7329; HR=0.997, 95% CI 0.982-1.013). The correlation between SCF and c-Kit is weak (0.39; 95% CI 0.06-0.63). Conclusions. c-Kit expression was not found to be associated with metastasis formation. A high SCF expression of primary choroidal melanomas was significantly associated with a lower incidence of systemic metastasis, which indicated SCF as a benign prognostic factor in the further clinical course.