PIK3CA and head and neck squamous cell carcinoma: We then compared the mutational profiles in ESCC, HNSCC, LUSCC or oesophageal adenocarcinoma (EAC) and found that the 20 genes significantly mutated in ESCC were also frequently mutated in HNSCC and LUSCC; however, in EAC, only TP53, CDKN2A and PIK3CA were frequently mutated (Supplementary Data 4).