It has been reported that when the tumor progresses after chemotherapy, the CTCs population also changes, with an enrichment in the CTCs of the expression levels of stemness and pluripotency genes such as CD44, ALCAM, EPCAM, NOTCH1, POU5FIB, and PTCH1, or CSC drivers as VEGFB and STAT3 [149]. This evidence concerns the gene CD44 and neoplasm.