CD44 and cancer: Interestingly, the expression of such markers is tumor subtype specific: CD44+CD−/low lineage and ALDH+ are abundant in breast CSCs [124,125], CD133+ for colon [126], brain [127] and pancreas [128], CD44+ for head and neck [129] and cervix [130], CD90+ for liver CSCs [131] and head and neck [132] cancers.