CD44 and breast cancer: The various combinations used to identify breast cancer stem cells (BCSCs) include CD44+/CD24−/low, aldehyde dehydrogenase (ALDH1), CD44+/CD49f+/CD133+, and epithelial cell adhesion molecule (EpCAM/CD326), all cell subpopulations that have been shown to have increased tumorigenic and metastatic potential [26,27] as well as also be involved in EMT.