A definite role of CD44 in sustaining GSC activity is still to be determined and it has been proposed that it may vary according to the location of CD44-positive GSCs within the tumor mass: CD44 is involved in the control of stemness in the cells present in hypoxic niches, while it favors their tissue dissemination if it is predominant in perivascular niche GSCs [148,149,150]. The gene discussed is CD44; the disease is neoplasm.