ALDH1A1 and head and neck squamous cell carcinoma: The aim of this research was to assess the expression of aldehyde dehydrogenase 1 (ALDH1) and epithelial-mesenchymal transition (EMT) markers in head and neck squamous cell carcinoma (HNSCC), and to correlate them with the clinical and histopathological parameters of a patient cohort with follow-up over an 8-year period.