Background Difficulties persist in differentiating pancreatic ductal adenocarcinomas (PDAC) from pancreatic inflammatory masses (PIM).Auxiliary diagnostic techniques which enhance the endoscopic ultrasound-guided fine-needle aspiration (EUS-FNA) diagnostic yield have been attempted,for example,K-ras mutation analysis.We aimed to evaluate the accuracy of K-ras mutation analysis combined with EUS-FNA for the differential diagnosis of PDAC and PIM by pooling data of existing trials.Methods We systematically searched the Medline,PubMed,Web of Science,Embase,and Cochrane Central Trials databases for relevant published studies.Meta-analysis was performed.Pooling was conducted in fixed-effect model or random-effect model.Results In total eight studies,with 696 cases of PDAC and 138 cases of PIM,met our inclusion criteria.The pooled sensitivity,specificity,positive likely ratio and negative likely ratio of K-ras mutation analysis combined with cytopathology for diagnosis of PDAC versus PIM were 90％,95％,13.45,and 0.13,respectively.Especially,among total 123 patients whose EUS-FNA results were inconclusive or negative,fifty-nine had K-ras mutations and were finally diagnosed with PDAC (48％,59/123).Publication bias was not present.Conclusions Combining K-ras mutation analysis with routine cytology moderately improves the ability of EUS-FNA to differentially diagnose between PDAC and PIM,especially for patients with suspected PDAC yet inconclusive EUS-FNA findings,and may prove to be a valuable supplemental method to EUS-FNA.