Though CD44 is generally accepted as a surrogate marker for head and neck squamous carcinoma cancer stem cells (HNSC CSCs) [32], in a recent study by Oh et al., in 2013, comparing in vitro stem-like cell characteristics, chemoresistance, and in vivo tumour formation capacity of CD44+ and CD44− HNSC cells obtained from primary HNSCC patient specimens, it was suggested that CSCs themselves hold the ability to be heterogenous due to various genetic alterations and hence cannot be used as a selective marker of spheroid-forming, tumour-initiating, or chemoresistant cell populations [44]. This evidence concerns the gene CD44 and head and neck squamous cell carcinoma.