These results are unlikely related to the potential bias inherent in the use of an arbitrary cut-off point, since clinical outcome was also studied utilizing the percentage of CD133 positive tumor cells as a continuous value; moreover, all patients were diagnosed, treated, and followed up at the same Institution, thus reducing the bias related to the differences in the extent of surgical cytoreduction or general management of this neoplasia. This evidence concerns the gene PROM1 and neoplasm.