KRAS and adenocarcinoma: Adenocarcinoma and PD carcinoma more commonly showed variants in genes involved in signal transduction pathways (e.g. MET, JAK3, EGFR, HRAS, KRAS and BRAF), whereas alterations in cell cycle control and DNA repair pathway genes (e.g. TP53, CDKN2A and MLH1) were more commonly seen in SCC.