CXCL9 and head and neck squamous cell carcinoma: Remarkably, only 20 GSTTKs were mutated and had a frequency greater than 1%, including NLRC5, GMIP, CXCL9, SFTPA2, COL23A1, MAP7D3, PSMB5, SOAT2, etc. They play an important role in the development and progression of HNSCC.