PIK3CA and head and neck squamous cell carcinoma: The cohort did not reveal any significant association between clinical features such as age, gender, tumor stage, American Joint committee on Cancer (AJCC) TNM stage, nodal status, smoking, alcohol, tobacco usages with mutations in HNSCC hallmark gene; TP53, NOTCH1, CDKN2A, CASP8, HRAS and PIK3CA (Supplementary Table S14).