Recent evidences suggest that BCSCs may form part of two interconvert dynamic mesenchymal-epithelial transition (MET)-EMT states that gives rise to more quiescent, mesenchymal-like BCSCs (CD44+/CD24−), localized at the tumor’s invasive front and more proliferative epithelial-like BCSCs (ALDH+), found more centrally within tumors [37]. The gene discussed is CD44; the disease is neoplasm.