CD44 and breast cancer: However, the optimal marker combinations are very dependent on the tissue and specific cell of origin of the tumor, and even well-established markers such as CD44+CD24−/lo for breast cancer and CD133+ for brain tumors do not robustly distinguish tumorigenic from nontumorigenic cells in all patient samples (Magee et al., 2012; Visvader and Lindeman, 2012).