PIK3CA and head and neck squamous cell carcinoma: The Cancer Genome Atlas (TCGA) Research Network (https://www.cancer.gov/about-nci/organization/ccg/research/structural-genomics/tcga) analyzed 530 tumor samples from HNSCC patients and identified the phosphatidylinositol 3-kinase (PI3K) signaling cascade as the most frequently altered pathway with a gain of function in more than 75% of cases.