To explore the clinical utility of liquid biopsy in cyst type classification, we analyzed the GNAS/KRAS mutations in circulating cell-free DNA (cfDNA) obtained from 57 patients with histologically diagnosed PCNs, including 34 with intraductal papillary mucinous neoplasms (IPMNs) and compared the mutant allele prevalence and variant patterns with the paired resected specimens using next-generation sequencing. The gene discussed is KRAS; the disease is cyst.