Chen et al. (2014) suggested that CD44 is related to worse T category, N category, tumor grade and prognosis in pharyngeal and laryngeal cancer, but no clear association was revealed between CD44 expression and oral cancer. Jakob et al. (2020) recommend testing for CSC markers in patients with advanced or late stage HNSCC, as they observed correlations between CSC markers ALDH1, BCL11B, BMI-1, and CD44 and prognosis. Here, ALDH1A1 is linked to head and neck squamous cell carcinoma.