CDKN2A and head and neck squamous cell carcinoma: While TP53, CCND1, CDKN2A, FGFR1, PIK3CA, and NOTCH are highly mutated in HPV-negative HNSCC [155], HPV positive HNSCC presents a higher mutational incidence of FGFR2, FGFR3, PIK3CA and KRAS genes [178].