Diagnostic Role and Therapeutic Perspectives of Endoscopic Ultrasound for Pancreatic Neuroendocrine Tumor

Abstract

Pancreatic neuroendocrine tumors (PNETs) are rare tumors with malignant potential, but their incidence has appreciably increased over the last few decades. Diagnosis of PNETs is often difficult with conventional imaging methods. Cross-sectional imaging localizes less than 10% of PNETs less than 1 cm in diameter. Endoscopic ultrasound (EUS) has been shown to be superior to other imaging techniques in the preoperative localization and diagnosis of PNETs. The finding of a hyperenhanced lesion on contrastenhanced EUS was highly predictive of PNETs different from adenocarcinoma. Preoperative assessment of tumor differentiation and Ki-67 is an important prognostic factor for grading. Thus, EUS-guided fine needle biopsy may play a key role in the work-up of nonfunctioning PNETs, and attempts to measure Ki-67 on cytologic and histologic samples have been made. According to the European Neuroendocrine Tumor Society guidelines, there is no clear evidence of a survival benefit of surgery for nonfunctioning G1 PNETs <2 cm in diameter. The benefits of curative surgery must be weighed against operative morbidity and mortality. Although surgical resection remains the mainstay for PNETs, EUS-guided ablation offers a relatively safe and effective treatment option in patients deemed unfit for, or who do not want to undergo, surgery. EUS-guided ablation provides an attractive therapeutic nonsurgical option for patients; however, further studies that better elucidate the long-term outcomes with standardization of technique will help define its role in the treatment of PNETs. The role of EUS in the diagnosis and treatment of PNETs is expected to make much progress in the future.