PIK3CA and head and neck squamous cell carcinoma: Other similarities were rare activating mutations in oncogenes PIK3CA and HRAS, deletions of CDKN2A and amplifications of CCND1, epidermal growth factor receptor (EGFR), MYC and PIK3CA. A complete listing of mutations identified in HNSCC cell lines in Barretina et al. is provided in Additional file 2: Table S2.