CD44 and breast carcinoma: In breast cancer, TAMs can promote BCSCs through a paracrine EGFR/Stat3/Sox-2 signaling pathway (67), while upregulation of HAS2 (hyaluronan synthase 2) in CD44+/CD24−/ESA+ BCSCs can enhance the interaction between BCSCs and TAMs, resulting in the BCSC growth (68).