CD44 and neoplasm: To date, the complement of surface markers utilized for the isolation of tumor initiating cells (also referred to as cancer stem or cancer initiating cells) from solid tumors have varied in breast (CD44+, CD24-/low, EpCAM+, Lineage- [36]), brain (CD133+ [18]), pancreas (CD44+/CD24+/EpCAM+ [37]), colon (CD133+ [20,38]) and prostate (CD44+/α2β1hi/CD133+ [19]) cancer.