Risk of malignancy and prognosis of sporadic resected small (≤2 cm) nonfunctional pancreatic neuroendocrine tumors.

Background: Small nonfunctional pancreatic neuroendocrine tumors (NF-PNETs) ≤2 cm have variable biological features, and there is no gold standard treatment for their management. The present study aimed to evaluate the risk of malignancy of small NF-PNETs and their outcomes following curative resection.

Methods: Patients with NF-PNETs undergoing surgical resection at the First Affiliated Hospital, College of Medicine, Zhejiang University, between 2012 and 2017 were included. Clinicopathological characteristics, perioperative results, and prognosis were retrospectively analyzed.

Results: A total of 73 patients were identified, including 28 with small NF-PNETs and 45 large PNETs; 32.1% of NF-PNETs ≤2 cm underwent a parenchyma-sparing pancreas surgery, which was >6.7% in large NF-PNETs. No statistically significant differences in perioperative results, postoperative complications, and long-term outcomes were found between small tumors undergoing standard and parenchyma-sparing pancreatectomy. Eighteen small tumors (64.3%) developed a perioperative complication, with a clinically significant pancreatic fistula rate of 25%; however, only 2 patient needed reintervention. Small NF-PNETs in 3 patients were malignant. Multivariate logistic regression showed that grade ≥3 and lymphovascular invasion were independently related to malignancy in NF-PNETs.

Conclusions: Small NF-PNETs (≤2 cm) are not immune from potential malignancy. Surgical resection may be considered for small tumors and can provide favorable postoperative and long-term outcomes. Parenchyma-sparing pancreatectomy may be an alternative surgery for selected small local NF-PNETs.