Background: This study aimed to evaluate potential difference in clinicopathological characteristics, prognosis as well as the genetic bases between insulinomas and non-functional pancreatic neuroendocrine neoplasms (NF-PNENs).

Methods: We analyzed data from 241 patients who underwent resection for PNENs measuring 1-2 ​cm at West China Hospital between 2002 and 2020.

Results: NF-PNENs were more likely to show lymph node involvement (P ​< ​0.001), perineural invasion (P ​= ​0.025), and a more advanced tumor grade (P ​< ​0.001). In multivariate analysis, NF-PNENs, when combined with lymph node metastasis and WHO G2/G3 grading, independently decreased recurrence-free survival [hazard ratio (HR), 4.72; P ​= ​0.014]. Whole exome sequencing revealed that most of the top 20 somatic mutated genes (90 ​%, 36/40) between insulinomas and NF-PNENs are different. Besides, all copy number variant (CNV) patterns were present in NF-PNENs, whereas insulinomas were more likely to exhibit CNV amplification.

Conclusions: Insulinomas and small NF-PNENs exhibit distinct tumor biology, prognosis, and genetic backgrounds, which may inform changes in surgical management and postoperative follow-up strategies for these patients.