This finding is reminiscent of the variable combination of expression between a stem cell marker (CD44) and other stem cell markers, as recently reported for head and neck squamous cell carcinoma, and fits with the hypothesis that CSC evolution is a continuous dynamic process, which constantly leads to new generations of CSCs with genetic and/or epigenetic changes favouring metastatic potential.13,64 Among all of the stem cell markers that we evaluated, only nestin was maximally expressed in 100% of metastasizing OSCCs. This evidence concerns the gene CD44 and head and neck squamous cell carcinoma.