Size of Pancreatic Cysts Strongly Influences the Diagnostic Yield of EUS-FNA

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Background: Pancreatic cysts are increasingly detected at a small size with the common use of cross-sectional imaging. Endoscopic ultrasound with fine needle aspiration (EUS-FNA) has been shown to be useful for distinguishing benign from mucinous cystic neoplasms (MCNs). Obtaining cyst fluid for analysis via FNA increases the diagnostic accuracy of the test over characterizing cyst morphology by EUS alone. Smaller cysts yield less fluid; however, it is not known how cyst size influences the diagnostic yield of EUS-FNA. Aim: We sought to determine the relationship between cyst size and the ability to obtain fluid via EUS-FNA and if EUS-FNA of sub-centimeter cysts alters patient management. Methods: We retrospectively analyzed our center's experience with EUS-FNA of pancreatic cysts. Cysts were grouped by size as measured by EUS: ≤ 0.5 cm, 0.6-0.9 cm, 1.0-2.0 cm and > 2.0 cm. For each patient, cyst diagnosis was determined by surgical pathology (when available) or via established criteria for diagnosis of MCNs by cyst fluid chemistry (CEA >192 ng/mL) and/or cytopathologic analysis. EUS-FNA was felt to change management if results of the examination lead to surgery, cyst ablation, increased frequency of imaging, or no further evaluation was deemed necessary. Results: We identified 194 consecutive patients who had EUS-FNA performed for the evaluation of pancreatic cysts. Mean age was 60 years and 59% of cysts were discovered incidentally. EUS-FNA was unable to obtain fluid in 38 patients (20%). By chi-square analysis, cyst size ≤0.5 cm, 0.6-0.9 cm, 1.0-2.0 cm, >2.0 cm strongly correlated with ability to obtain fluid (29, 75, 86, 94%, respectively; p < 0.0001), make a definitive diagnosis (0, 31, 59, 71%, respectively; p ≤ 0.0001), alter management (0, 0, 17, 35%, respectively; p = 0.002), refer for surgery (0, 0, 10, 24%, respectively; p = 0.02) and diagnose MCNs (0, 8, 44, 38%, respectively; p = 0.02). This relationship was independent of age, gender, the presence of symptoms, and location of the cyst. Five cancers (2.6%) were diagnosed, all of which were >2.0 cm (range 2.5-10.0 cm). Conclusion: This is the first study to our knowledge to demonstrate that cyst size strongly correlates with the ability of EUS-FNA to accurately diagnose pancreatic cysts and identify MCNs. EUS-FNA provides excellent yield for cysts ≥1.0 cm with a diagnosis being made in the majority of patients and a clinically significant number of patients having their management altered after the procedure. Due to limitations in obtaining adequate fluid for analysis, performing EUS-FNA in cysts ≤0.5 cm does not lead to a change in management.