Diagnostic accuracy and risk stratification of pancreatic cyst fluids diagnosed as mucinous neoplasms without mucinous epithelium.

INTRODUCTION

Neoplastic mucinous cysts (NMC) are premalignant lesions that can be diagnosed on pancreatic cyst fluid (PCF) based on elevated carcinoembryonic antigen or thick extracellular mucin (ECM) without mucinous epithelium. Under the World Health Organization classification, such cases are considered "pancreaticobiliary neoplasm, low-risk/grade." This study evaluates the diagnostic accuracy and risk of cysts diagnosed as NMC without mucinous epithelium.

MATERIALS AND

METHODS

A total of 609 PCF specimens (493 patients) diagnosed as NMC were identified; 279/609 (45.8%) had no mucinous epithelium: 182 and 61 were diagnosed based only on elevated carcinoembryonic antigen ≥192 ng/mL or ECM, respectively.

RESULTS

Among PCF without mucinous epithelium and with molecular correlation, 110/165 (66.7%) harbored KRAS/GNAS/RNF43 mutations. High-risk mutations (TP53/CDKN2A/SMAD4) occurred at similar rates in cysts with low-grade mucinous epithelium as in those without mucinous epithelium (6.5% vs. 3.6%, p = .224). A total of 63/71 (88.7%) resections from cysts without mucinous epithelium were confirmed as NMC: 40 (56.3%) had low-grade dysplasia and 23 (32.4%) had at least high-grade dysplasia. A total of 142/279 (50.9%) PCF without mucinous epithelium were molecularly or histologically confirmed as NMC. No significant differences were found in the rates of new worrisome radiologic features, invasive carcinoma, or disease-related mortality between the groups. Patient survival trended lower in the cohort with mucinous epithelium, though rates were comparable upon subanalysis of only "pancreaticobiliary neoplasm, low-risk/grade" cysts.

CONCLUSIONS

Even though PCF diagnosed as NMC without mucinous epithelium defaults to a low-risk category, the rates of high-grade neoplasia/high-risk outcomes are comparable to those with low-grade mucinous epithelium, supporting continued utility of carcinoembryonic antigen and ECM as diagnostic criteria for NMC in the absence of mucinous epithelium.