CD44 and breast carcinoma: Another very notable example of this situation in breast cancer is that of the MDA-MB-231 cell line; data reported here and by others has shown that in excess of 99% of the total cell population express the CD44+CD24−/low marker signature that is supposed to describe highly tumourigenic breast CSC, yet only a minority fraction of the cell population possesses the ability to initiate population re-growth [39].