However, here we show that previously identified CSC markers (e.g., CD34+CD38− for AML, APL, and CML, CD44+CD24− for breast cancer, CD133+ for glioblastoma and colon cancer, CD271+ for melanoma) do not necessarily filter out tumorigenic cells in these tumors, because both CSC+ and CSC− cells can initiate tumor growth and give rise to both progenies (ie, CSC+ and CSC− cells). This evidence concerns the gene CD44 and breast carcinoma.