To date, CSCs have been isolated based on their ability to express specific cell surface molecules in hematologic malignancies and epithelial-cell-derived cancers, including acute myeloid leukemia (CD34+CD38−CD123+) [5], mammary carcinoma (CD44+CD24low) [6], brain tumors (CD133+) [7], colon cancer and melanoma (CD133+) [8]–[11]. The gene discussed is PROM1; the disease is breast carcinoma.