PIK3CA and neoplasm: Moreover, his tumor also lacked the most common somatic mutations of HNSCC, such asTP53,NOTCH1,CKDN2A,PIK3CA (phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit alpha) andFAT1 (FAT atypical cadherin 1)5,11,12.