PIK3CA and esophageal squamous cell carcinoma: Through analyzing 51 sub-tumor regions from 13 ESCC patients, Hao et al. [42] proposed that approximately 40% of driver mutations were spatially heterogeneous, including oncogenes such as KIT, and members of the PI3K/MTOR (PIK3CA and MTOR) and NFE2L2 pathways (NFE2L2 and KEAP1).