ALDH1A1 and oropharynx squamous cell carcinoma: Increased ALDH1A1 expression in HNSCC correlates with a low degree of tumor cell differentiation, metastasis to lymph nodes, and duration of a recurrence-free period [40], which allowed us to propose ALDH1A1 as a prognostic biomarker for oropharyngeal squamous cell carcinoma [41].