Su1370 A Novel Algorithm for the Prediction of Malignancy in Patients Undergoing EUS-FNA of Pancreatic Cystic Lesions

Background: Endoscopic ultrasound guided fine needle aspiration (EUS-FNA) to obtain cyst wall cytology and fluid analysis is increasingly being utilized to differentiate between mucinous, non-mucinous, and malignant pancreatic cystic lesions.While an elevated cyst fluid carcinoembryonic antigen (CEA) is predictive of a mucinous pancreatic cyst, cytology alone remains a poor predictor of malignancy.Aim: To determine whether EUS-guided cyst fluid analysis in addition to cyst wall cytology correlates with pancreatic cyst pathology.Methods: We conducted a retrospective, multicenter study of all patients who underwent EUS-FNA of a pancreatic cyst prior to surgical resection from 2005 to 2015.Cysts were subclassified as mucinous cystic neoplasms (MCN) or intraductal papillary mucinous neoplasms (IPMN) by surgical pathology; all other cysts were excluded.Cyst wall cytology was correlated with final surgical pathology.Pancreatic cyst fluid CEA and amylase were sent for analysis when sufficient samples were available.Results 271 patients were included.The mean cyst size was 24.2mm (±12.5mm).Pancreatic cysts were located in the head in (54.6%) patients and in the body/tail in (45.4%) patients.Cyst fluid CEA was obtained in 257 (94.8%) and amylase in 251 (92.6%) patients.Cytology was indeterminate in 134 (49.4%),mucinous in 101(37.3%),and mucinous with advanced features in 36 (13.2%)of cases.The post-surgical histology showed MCN in 30 (11.2%) patients and IPMN in 239 (18.9%).82 (30.3%) patients had worrisome features on EUS including mural nodules (n=25), solid component (n=27), debris (n=25), dilated MPD (n=5); these findings were not associated with final histology (p=0.40).The operating characteristics of a positive EUS-FNA of cyst wall to diagnose a malignant cyst was as follows: sensitivity=24%, specificity=72%, PPV=22%, NPV= 74% and a diagnostic accuracy of 60.7% with an ROC of 0.48.The operating characteristics of EUS-FNA of the cyst wall in addition to an evaluated CEA>300 was as follows: sensitivity= 66%, specificity=63%, PPV=22%, NPV=92%, and a diagnostic accuracy of 64% with an ROC of 0.65 (figure 1).Conclusion In this multicenter study, a pancreatic cyst fluid of CEA >300 in addition to positive EUS-FNA cytology were a strong predictor of malignancy when compared to a positive cytology alone.