BRAF and head and neck squamous cell carcinoma: In HNSCC, activating mutations in KRAS, NRAS, and BRAF are rarely observed, and though activating mutations in HRAS have been implicated in cetuximab resistance in HNSCC [22,23], HRAS alterations are observed in only 5% of HNSCC tumors and its robustness as a negative predictive biomarker remains unproven [6].