DDR2 and head and neck squamous cell carcinoma: For instance, HPV-negative HNSCC has a higher number of mutations in TP53, CDKN2A, MLL2, CUL3, NSD1, FGFR1, DDR2, EGFR, FGFR2/3, EPHA2, PIK3CA and NOTCH genes; while HPV-positive cases present mutations in genes such as DDX3X, FGFR2/3, PIK3CA, KRAS and MLL2/3 [33].