CD44 and breast neoplasm: Subsequent to the discovery that the combination of two markers, CD44 and CD24, can define and enrich for an important stem cell population in breast tumours by flow cytometry [1], others demonstrated that the addition of a third marker to this combination could further purify cells with different functional characteristics, namely EpCAM+/CD44+/CD24−[13] and Aldefluorbri/CD44+/CD24−[41].