ALDH1A1 and oral cavity squamous cell carcinoma: The evidence so far, regarding the biomarker ALDH1&2, includes the following observations: ALDH has increasingly been used as a CSC marker in oral cavity squamous cell carcinoma (OCSCC), with ALDH+ cells demonstrating plasticity with the ability to form tumor spheres in serum-free media as well as having the ability to generate ALDH cells in vitro [14].