Usefulness of EUS combined with contrast-enhancement in the differential diagnosis of malignant versus benign and preoperative localization of pancreatic endocrine tumors

Background: Pancreatic endocrine tumors (PETs) develop in relatively few patients, but they are often difficult to diagnose because of their small size and various clinical symptoms. Objective: The aim of this study was to investigate the usefulness of EUS combined with contrast enhancement (CE-EUS) in the preoperative localization of PETs and the differentiation between malignant and benign PETs. Design and Setting: Single-center retrospective study. Patients: Sixty-two pathologically certified PETs of 41 patients who underwent EUS, multiphasic multidetector computed tomography (MDCT), and transabdominal US at our institute since 2001. Interventions: Intravenous injection of US contrast media. Main Outcome Measurements: Comparison of EUS, MDCT, and US in the preoperative identification of PETs, and the characteristic findings of EUS with malignancy. Results: EUS showed high sensitivity (95.1%) in identifying PETs compared with MDCT (80.6%) and US (45.2%). Multivariable logistic regression analysis showed that heterogeneous ultrasonographic texture was the most significant factor for malignancy (OR = 53.33; 95% CI, 10.79-263.58). Most heterogeneous hypoechoic areas and anechoic areas corresponded to hemorrhage or necrosis on pathologic examination. They were identified as filling defects in CE-EUS and were more clearly recognized than in conventional EUS. Limitations: Retrospective study. Conclusion: EUS has higher sensitivity in preoperative localization of PETs compared with MDCT and US. The characteristics of EUS and CE-EUS findings in malignant PETs were clarified, and they will improve the diagnostic accuracy of PETs.