Cyst fluid analysis obtained by EUS-guided FNA in the evaluation of discrete cystic neoplasms of the pancreas: a prospective single-center experience

Background Accurate assessment of pancreatic cystic neoplasms is imperative before selecting available treatment options, such as surgical resection, drainage, or conservative therapy. Available modalities, CT and magnetic resonance imaging, have been inconsistent in diagnosis. Reports involving EUS and cyst fluid analysis have been encouraging, including studies of EUS features and/or cyst fluid analysis, which may differentiate pancreatic cystic neoplasms. Objective To retrospectively determine cyst fluid characteristics that differentiate cystic neoplasms. Methods A total of 102 patients (60 women, 42 men; age, 23-76 years) presented for evaluation of pancreatic cystic neoplasm; 71 underwent surgical resection. Evaluation included (1) EUS features (reported elsewhere) and (2) cyst fluid analysis (carcinoembryonic antigen [CEA], carbohydrate antigen 19-9 [CA 19-9], amylase and lipase, viscosity [VIS], mucin stain, and cytology). Exclusion criteria included the following: intraductal papillary mucinous tumor lesions, bloody cyst aspirate, neuroendocrine tumors, and patients without surgical histopathology. Results Seventy-one of 102 patients who underwent surgery presented the following histopathologic correlates: 23 pseudocysts (PC), 13 serous cystadenoma (SCyA), 21 mucinous cystadenoma (MCyA), and 14 mucinous cystadenocarcinoma (MCyA-CA). Cyst fluid analysis of these patients showed the following: VIS was lower in PC (mean, 1.3) and SCyA (1.27) when compared with MCyA (1.84) and MCyA-CA (1.9). All mucinous neoplasms had VIS >1.6, whereas only 2 nonmucinous neoplasms (MCN) had VIS = 1.6 (both PC). The CEA level was significantly higher in MCyA (adenoma [878 ng/mL], carcinoma [27,581 ng/mL]) vs PC (189 ng/mL), and SCyA (121 •••). Amylase levels were higher in PC (7210 U/L) compared with cystic neoplasm (SCyA, 679 U/L; MCyA, 1605 U/L; MCyA-CA, 569 U/L). Conclusions Differential diagnosis of pancreatic cystic neoplasm is significantly enhanced by cyst fluid analysis. Elevated CEA (≥480 ng/mL) and VIS (>1.6) accurately predict MCN from SCyA and PC. Malignant from benign MCN can be differentiated by CEA levels ≥6000 ng/mL.