PIK3CA and esophageal squamous cell carcinoma: Other amplified genes involved in ESCC are MYC (8q24.21), KRAS (12p12.1), MDM2 (12q15), PIK3CA (3q26.32), YAP1 (11q22.1), CBX4 and CBX8 (17q25.3) [25,29,31,56].