PIK3CA and esophageal squamous cell carcinoma: Moreover, several driver mutations that were found in all tumor cells among these 21 ESCC genomes can be placed on the shared trunk of the phylogenetic tree, including mutations of TP53, CDKN2A, AJUBA, PIK3CA, NOTCH1, FBXW7, RB1, FAT1, and ZNF750. Identifying trunk mutations can be helpful because targeting subclonal alterations would likely be less effective compared with therapies targeting true founding clone alterations [5, 7, 31, 32].