The results obtained in this study are not in agreement with those reported by Wright et al (12), who analyzed the breast cancer cell line RP.1 by flow cytometry and observed that only a small percentage (2.0–5.9%) of the cells expressed CD133, or with the findings of Dou et al (13), who analyzed CD133 expression in the B16F10 murine melanoma cell line and reported a low expression of CD133+ (3.40%) using the Magnetic Activated Cell Sorting (MACS) technique. The gene discussed is PROM1; the disease is breast carcinoma.