PIK3CA and esophageal squamous cell carcinoma: Univariate Cox showed that p-PI3K (P < 0.001), Ki-67 (P < 0.001), lymphatic metastasis (P < 0.001), differentiated (P < 0.001), nerve invasion (P = 0.004), treatment (P = 0.018), and AJCC (P < 0.001) were prognostic factors for ESCC, while GPNMB (P = 0.056), EGFR (P = 0.466), tumour size (P = 0.127), location (P = 0.760), infiltration depth (P = 0.275), vascular invasion (P = 0.064), age (P = 0.887), gender (P = 0.096), and nationality (P = 0.938) were not statistically significant (Table 2).