Background: Endoscopic ultrasound (EUS) with EUS-guided fine needle aspiration (EUS-FNA) has been increasingly utilized to differentiate 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 to distinguish mucinous cystic neoplasms from non-mucinous cystic neoplasms based on histopathology following surgical resection.

Methods: A retrospective, single center case series. Methods: Patients who underwent EUS and EUS-FNA of known or suspected pancreatic cysts followed by surgical resection. The final diagnosis was based on histopathology. Methods: Patients were divided in two groups: mucinous cystic neoplasms and non-mucinous cystic neoplasms. Patients with intraductal papillary mucinous tumors were excluded. Methods: Clinical profiles and EUS findings.

Results: Forty-eight patients (mean age: 52 years; 29 females, 19 males) were identified: 16 mucinous cystic neoplasms and 32 non-mucinous cystic neoplasms. There were more women in the mucinous cystic neoplasm group compared to the non-mucinous cystic neoplasm group (88% vs. 47%; P=0.011) but the two groups were otherwise similar. The sensitivity, specificity and frequency of cases correctly identified of EUS-FNA cytology for the diagnosis of mucinous cystic neoplasms were 12.5% (95% CI: 2.2-37.2%), 90.6% (95% CI: 75.0-97.5%) and 64.6% (95% CI: 50.4-77.0%), respectively. Median cyst fluid CEA for the mucinous cystic neoplasm group (277 ng/mL; n=14) was significantly higher (P=0.002) than the non-mucinous cystic neoplasm group (1.5 ng/mL; n=21). Cyst fluid CEA greater than 800 ng/mL had a sensitivity of 42.9% (95% CI: 21.3-67.4%) and specificity of 95.2% (95% CI: 75.6-99.9%) for the diagnosis of mucinous cystic neoplasm. On the other hand, a cyst fluid CEA greater than a best cut-off ranging from 3.5 to 8.5 ng/mL had a sensitivity of 92.9% (95% CI: 66.5-100%), a specificity of 66.7% (14/21; 95% CI: 45.2-83.0%), and an accuracy of 81.1% with a frequency of cases correctly identified of 77.1% (95% CI: 60.7-88.2%).

Conclusions: EUS-FNA cytology and cyst fluid CEA greater than 800 ng/mL are insensitive but highly specific for differentiating mucinous cystic neoplasms from non-mucinous cystic neoplasms. EUS morphology alone cannot distinguish between the two groups.