CD44 and neoplasm: With regard to the tumor-initiating ability in immune deficient mice, the number of CD24- CD44+ BCSCs was 100 cells, compared with 500 cells in ALDH+ BCSCs, while BCSCs expressing both CD24- CD44+ and ALDH+ phenotypes only needed 20 cells to generate tumors, indicating its most remarkable stemness features [11, 13].