Notably, nonsynonymous mutation and copy number loss/gain in TP53, KMT2D, NOTCH1, PIK3CA, and FAT1 in ESCC are frequently reported and discussed, as they played important roles in NOTCH signaling, the RTK-MAPK-PI3K pathway, and cell cycle regulation, all of which were closely related to tumor development and differentiation [7–9]. The gene discussed is PIK3CA; the disease is esophageal squamous cell carcinoma.