Endoscopic ultrasound guided - fine needle aspiration (EUS-FNA), in comparison with gross and histologic diagnoses of pancreatic lesions

EUS-FNA of the pancreas is the preferred method of investigating and diagnosing pancreatic masses, both solid and cystic. Most solid tumors of the pancreas are conventional pancreatic ductal adenocarcinomas (PDAC). EUS-FNA has a variable sensitivity but high specificity in the preoperative diagnosis of pancreatic lesions, although the diagnosis for well differentiated PDAC is much more challenging than for poorly differentiated PDAC. The criteria for distinguishing other solid neoplastic lesions from PDAC are reviewed. Contamination by duodenal or gastric epithelium is a common pitfall in the diagnosis of the two most common cystic lesions, intraductal papillary mucinous neoplasm and mucinous cystic neoplasm. In this review, based on our experience, we highlight and discuss the cytologic criteria for the diagnosis of pancreatic lesions, correlate these with the gross and histologic appearance, and discuss ancillary tests including KRAS and GNAS mutations, diagnostic pitfalls and future perspectives. Future studies on identifying and validating more sensitive and specific molecular markers are necessary to improve the EUS-FNA diagnosis of pancreatic lesions.