Although our previous study has demonstrated varied frequencies of expression of melanoma stem cell markers at different stages of the disease and site of the tumor tissue (10), our present study clearly delineates clonal dominance of CD133 in tissues of patients with primary melanoma who had disease progression or disease recurrence in comparison with primary melanoma with no recurrence, suggesting that the CD133 subset may be a determinant of tumor metastasis/tumor relapse. This evidence concerns the gene PROM1 and melanoma.