CD44 and head and neck squamous cell carcinoma: CD44 was used to assess the metastatic potential of HNSCC CSCs in both an in vitro and in vivo study showing no difference in metastatic ability in vitro but found CD44high cells resulted in lung lesions, when injected in tails of NOD/SCID mice about 50% of the time compared to 0% for CD44low cells [51].