PIK3CA and esophageal squamous cell carcinoma: In view that high expression of PI3K-p85α, EGFR and p53 were frequently detected in ESCC tumors but rarely in the adjacent normal esophageal tissues and the three-protein panel (PI3K-p85α/EGFR/p53) may be potentially applied to preoperative biopsies to provide the complementary basis for the diagnosis of ESCC.