THY1 and familial pancreatic carcinoma: Markers, and combinations of markers, which are used to isolate CSCs are currently chosen with respect to their heterogeneous expression in tumor tissues and not due to insight into a functional hierarchy of stem cells, for instance, CD24 and CD44 in breast cancer [9] and pancreas carcinoma [29], CD90 on hepatocellular carcinoma [30], CD133 in colon, lung, brain tumors [31-35], and EpCam in colorectal and pancreatic cancer [29, 36].