CD44 and breast cancer: For testing the hypothesis that MDA-MB-231 cell lines possess a high proportion (>90%) of CD44+/CD24- cells, MDA-MB-231, MCF-7 cell lines, and normal breast cells (separated from reduction mammoplasty material) were assessed via flowcytometry to investigate the expression of CD24 and CD44 surface proteins, which have a main relation with breast cancer stem cell markers.