HRAS and head and neck squamous cell carcinoma: In a study of 51 patients with HNSCC (with higher prevalence in the larynx and trachea area), mutations of the KRAS gene (sometimes designated KRAS1 or KRAS2) were detected in 35% of cases, and mutations of the HRAS gene in 33% of cases, with the caveat that KRAS mutations, HRAS mutations, and HPV infection are mutually exclusive (68).