KRAS and esophageal squamous cell carcinoma: Furthermore, mutations in ESCC patients have been recently reported; 16% of ESCC patients (5/30 cases) harbor K-ras gene mutations [36], 14% of ESCC patients (7/50 cases) contain EGFR mutation [37], and 2.2-11.8% of ESCC patients have gene mutations in exon 9 of the PIK3CA gene [38,39].