ALDH1A1 and head and neck squamous cell carcinoma: CSC markers ALDH1A1, CD44, BMI1, OCT4, SOX2, and CD133 and their effects on cancer stemness, metastasis, prognosis, chemo/radiotherapy resistance and recurrence have been studied in HNSCC by our group and other researchers [10,17,22,31,32,33,34,35,36,39,40,41,42,45,46,48,49,50,52,53,54].