PIK3CA and head and neck squamous cell carcinoma: Extensive exome-wide studies in SCCHN have been reported12, 19, 20, uncovering recurrent somatic mutations in TP53 (47–72%), NOTCH1 (14–19%), CDKN2A (9–22%), PIK3CA (6–21%), FBXW7 (5%), HRAS (4–8%) and CASP8 (8%).