Cancer stem cells (CSC) are the tumor-associated cells existed within tumors or hematological cancers which share characteristics similar to normal stem cells. The common characteristics of a normal stem cell and a CSC are their differentiation capacity and self-renewal in tumors. The expression pattern of CSC markers differs depending on the type and location of cancers. CD molecules are probably the most common biomarkers for CSCs. CD molecules such as CD133, CD24, CD44, CD138 and similar CD

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... olecules are well known markers for identification of CSCs. In addition, ATP-Binding Cassette (ABC) transporters such as ABCG2 and ABCB5 as well as EpCAM, ALDH1 and CXCR4 have been used to identify certain CSCs. Therefore these markers may be considered specific for better identification and diagnosis of a specific tumor. Currently studies are in progress to find new cell surface markers which can distinguish specific markers from other markers for isolation and characterization of CSCs. The future of this area of research is promising in developing novel prognostic assays and therapeutic approaches based on cellular and signaling functions of these markers.