In total, 27 commercially available cell lines derived from normal and malignant mammary tissue were characterized into differentiated tumor cells and/or BCSC subpopulations (ALDH−CD44+CD24-/low enriched mesenchymal-like BCSCs, ALDH+non-CD44+CD24−/low enriched epithelial-like BCSCs, and highly purified ALDH+CD44+CD24−/low BCSCs). The gene discussed is CD44; the disease is neoplasm.