Comparison of EUS Morphology and Performance of EUS-FNA for Benign and Malignant Pancreatic Neuroendocrine Tumors

Abstract

Introduction: Pancreatic endocrine tumors (PET) are rare neoplasms frequently evaluated by EUS yet there are limited data comparing EUS findings and sensitivity of EUS-guided fine needle aspiration (EUS-FNA) in benign and malignant tumors. Aim: To compare EUS morphology and sensitivity of EUS-FNA between benign and malignant PET. Methods: We retrospectively identified all patients from 7/95 to 11/06 who underwent EUS for suspected or subsequently confirmed PET. All patients had a pancreatic mass visible by EUS. The diagnosis of a PET was confirmed by: 1) EUS-FNA with (after 1999) or without (before 1999 when test not routinely performed) confirmatory immunochemistry (ICC) with synaptophysin and/or chromogranin of ≥ 1 pancreatic mass or metastatic site; or 2) an alternative biopsy procedure and/or surgical resection of the pancreas or other metastatic site. Patients without positive ICC were required to have biopsy or surgical resection from a pancreatic or extra-pancreatic site to confirm the diagnosis. Malignant PET was defined as tumors that originated in the pancreas with any evidence of tumor beyond the primary pancreatic site. Results: 76 patients (53 male; median age: 57 yrs, range 23-83 yrs) with 36 (47%) benign and 40 (53%) malignant PET were identified. Malignant PET patients were older by an average of 7 years (58 vs. 51 yrs, p=0.03). Benign tumors were more likely to present with hypoglycemia (p=0.02) whereas malignant tumors tended to present with abdominal pain (p=0.007). By EUS, the tumors were located in the pancreatic head, body, tail or were multifocal in 35 (46%), 21 (28%), 15 (20%) and 5 (6%), respectively. Tumor location within the pancreas was similar between benign and malignant PET (head: p=0.11, body: p=0.61, tail: p=0.77). Compared to benign tumors, malignant PET were larger (median diameter: 31 vs. 19mm; p=0.0006) and were more likely to have irregular margins (50% vs. 25%; p=0.03). Echogenicity was similar between both groups (p=1.0). EUS-FNA of a pancreatic mass was performed in 68 (89%) of the 76 PET with subsequently confirmed histopathology. The sensitivity of EUS-FNA for the diagnosis of malignant PET 95% (CI: 81-99%) was greater than that for benign PET 77% (CI: 60-89%; p=0.009) Conclusion: In this single center study of patients undergoing EUS for confirmed PET, patients with malignant PET were more likely to be older, present with abdominal pain and have larger tumors with irregular borders compared to those with benign tumors. The sensitivity of EUS-FNA for the diagnosis of malignant PET is higher than that for benign PET.