PIK3CA and head and neck squamous cell carcinoma: The phosphatidylinositol 3‐kinase (PI3K) signaling pathway is the most frequently altered oncogenic pathway in HNSCC (Du et al., 2012; Iglesias‐Bartolome et al., 2013; Lui et al., 2013; Pickering et al., 2013; The Cancer Genome Atlas, 2015; Vander Broek et al., 2015).