PGC and chronic atrophic gastritis: This study, for the first time, reports that pri-let-7a-1 rs10739971 polymorphism and ERCC6 rs1917799 polymorphism might have an interaction effect on gastric cancer risk; and pri-let-7a-1 rs10739971 polymorphism might have an interaction effect with PGC rs6458238 and rs9471643 polymorphisms on atrophic gastritis risk.