In HNSCC, ALDH1 (Aldehyde dehydrogenase 1), BMI-1 (B-lymphoma Moloney murine leukemia virus insertion region-1), and CD44 belong to the most studied CSC markers and, additionally, BCL11B (B-cell lymphoma/leukemia 11B) was found to be a CSC marker in strong co-expression to BMI-1 [13,14,15]. Here, ALDH1A1 is linked to head and neck squamous cell carcinoma.