ALDH1A1 and head and neck cancer: Recent studies have pointed out resistance to conventional radiotherapies/chemotherapies treatment is a major clinical criteria for characterizing cancer stem cells (CSCs) with self-renewal and highly tumorigenenic capacity in malignant tumors including HNC[2]–[4] Both intracellular ALDH1+ and CD44+ cells have been proposed to exhibit CSCs properties and have been used as CSCs functional markers for head and neck cancer-derived cancer stem cells (HNC-CSCs)[5]–[7].