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 follow-up (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.