Utility of EUS-FNA and Cyst Fluid Analysis in the Diagnosis of Pancreatic Cysts: Correlation with Histopathology in 51 Patients

Background: Endoscopic ultrasound (EUS) with EUS-guided fine needle aspiration (EUS-FNA) have been increasingly utilized for differentiating malignant/pre-malignant pancreatic cysts from those that are benign or have low malignant potential. Objective: To determine the utility of EUS morphology, EUS-FNA cytology and cyst fluid analysis in distinguishing mucinous cystic neoplasms (MCNs) from non-mucinous cystic neoplasms (NMCNs) in patients with histopathologic correlation. Methods: Endoscopy, cytology and surgery databases at our hospital from 1996 to 2005 were queried for all patients who underwent EUS evaluation of known or suspected pancreatic cysts followed by surgical resection. Clinical profiles and procedure reports were reviewed and compared between both groups. The final diagnosis in all patients was based on histopathology. Patients with intraductal papillary mucinous tumors were excluded. Results: 51 patients (mean age: 51 yrs, 32 female) with 16 MCNs (13 mucinous cystadenomas [MCAs], 3 mucinous cystadenocarcinomas [MCACs]) and 35 NMCNs (14 pseudocysts, 10 serous cystadenomas, 5 simple cysts, 3 neuroendocrine tumors, 3 solid pseudopapillary neoplasms. Mean time between EUS and surgery was 65 days. Abdominal pain (the most common symptom) was reported in 32 (63%) and 11 (22%) cysts were incidentally found. In 45 patients with available history, antecedent pancreatitis was present in 10 (22%). There were more women in MCN group compared to the NMCN group (87% vs. 51%; p = 0.02). For same groups, however, there were no statistically significant differences in mean age, median time from onset of symptoms, previous history of pancreatitis, or number of asymptomatic patients. Similarly, between both groups EUS morphology showed no statistically significant difference between the number and location of cysts, cystic components, cyst wall thickness, internal cystic echogenicity, or cystic fluid appearance. The sensitivity, specificity, PPV, NPV and accuracy of EUS-FNA cytology for the diagnosis of all MCNs (MCAs and MCACs) was 13%, 94%, 50%, 70%, and 67% respectively. Median cyst fluid CEA for the MCNs group (276.7 ng/ml; range: 0.5-144,000; n = 14) was significantly higher than the NMCN group (1.5 ng/ml; range: 0.5-2, 243; n = 21; p = 0.001). Cyst fluid CEA >800 ng/ml had a sensitivity and specificity of 43% and 95%, respectively for the diagnosis of an MCN. Pancreatic fluid amylase <10,000 U/L virtually excluded pancreatic pseudocyst. Conclusions: In this series of histopathologically confirmed pancreatic cysts, EUS-FNA cytology and cyst fluid CEA >800 ng/ml are both insensitive but very specific to differentiate MCNs from NMCNs.