PROM1 and cancer: To better elucidate the association between the prognosis of ER+/HER2− BC and the CSC surface marker CD133, we utilized two distinct cohorts: The Cancer Genome Atlas (TCGA) cohort, which includes 1065 breast cancer patients, and the Molecular Taxonomy of Breast Cancer International Consortium (METABRIC) cohort, consisting of 1904 breast cancer patients.