MYL9 and head and neck squamous cell carcinoma: The first scRNA‐seq of human head and neck squamous cell carcinoma (HNSCC) identified three distinct CAF subpopulations: myCAFs, expressing high levels of ACTA2 and MYL9, classic CAFs, marked by receptor and ECM‐related genes, including FAP, PDPN and CTGF, or resting CAFs, which was lack of myCAF and classic CAF markers.101