Impact of endoscopic ultrasound fine-needle biopsy on management of suspected small (11-20 mm) and very small (≤ 10 mm), low-risk, non-functioning pancreatic neuroendocrine tumors

: Background and study aims The need for routine EUS-FNB of small (≤20mm) non-functioning pancreatic neuroendocrine tumors (NF-PanNETs) remains debated. We aimed to evaluate the impact of EUS-FNB on clinical management in patients with very small (≤10mm) and small (11-20mm) suspected NF-PanNETs who were otherwise suitable for active surveillance. Patients and methods Retrospective analysis of patients with single, sporadic, ≤20mm lesions, exhibiting typical imaging features of NF-PanNET, referred for EUS-FNB at two high-volume centers between January 2017 and December 2024. The primary outcome was the impact of EUS-FNB on management, defined as a diagnosis leading to a strategy other than active surveillance. Secondary outcomes included factors associated with a substantial management change, sample adequacy, safety, Ki-67 assessment, and concordance between EUS-FNB and surgical grading. Results Overall, 417 patients (160 with very small and 257 with small lesions) were included. EUS-FNB changed management in 68 cases (16.3%), more frequently in small than in very small lesions (19.8% vs. 10.6%; P=0.014). A substantial impact leading to surgical resection was more frequent in small lesions (12.4% vs. 3.7%; P=0.002). Lesion size 11-20mm was independently associated with a substantial impact (OR 3.19, 95%CI 1.05-9.66). Sample adequacy was 96.1%, adverse events rate was 3.4%, Ki-67 was feasible in 96.0% of confirmed PanNETs, and grading concordance with surgical specimens was 78.1%. Conclusions In patients with suspected small NF-PanNETs without suspicious features, EUS-FNB provides a clear clinical benefit for larger lesions. For very small (≤10mm) lesions, its more limited impact supports an individualized, shared decision-making with the patient.