Initial studies identified CD133 as a putative marker for GSCs [11, 12]; however, recent studies indicate that CD133 negative stem cells also harbor tumor initiating capacity [13, 14] and additional markers such as SSEA-1/CD-15, L1CAM, A2B5, CD90 and CD44 have been proposed [13, 15-17]. The gene discussed is CD44; the disease is neoplasm.