Original article Surgical strategies for non-functioning pancreatic neuroendocrine tumours M. J. Kim 1 , D. W. Choi 2 , S. H. Choi 2 , J. S. Heo 2 , H. J. Park 2 , K. K. Choi 2 , K.-T. Jang 3 and J.-Y. Sung 3 1 Department of Surgery, Jeju National University Hospital, School of Medicine, Jeju National University, Jeju, Korea, Departments of 2 Surgery and 3 Pathology, Samsung Medical Centre, Sungkyunkwan University School of Medicine, Seoul, Korea Correspondence to: Dr D. W. Choi, Department of Surgery, Samsung Medical Centre, Sungkyunkwan University School of Medicine, 50 Irwon-dong, Gangnam-gu, Seoul 135-710, Korea (e-mail: dw7722.choi@samsung.com) Background: The purpose of this study was to identify management strategies for non-functioning pancreatic neuroendocrine tumours (NF-PNETs) by analysis of surgical outcomes at a single institution. Methods: Archived records of patients with NF-PNETs who underwent surgery between 1994 and 2010 were reviewed. Results: Among 125 patients, the median tumour size was 2·5 (range 0·15–20·5) cm. Of the 51 NF- PNETs with a diameter of no more than 2 cm, 12 (24 per cent) were diagnosed as carcinoma. Overall 20 patients (16·0 per cent) had metastases to the lymph nodes. The minimum size of the tumour with lymph node metastasis was 1·2 cm. Having a NF-PNET of 2 cm or larger significantly increased the probability of a poorly differentiated carcinoma (P = 0·006), and having a NF-PNET of at least 2·5 cm significantly increased the probability of lymph node metastasis (P = 0·048). The 5-year cumulative survival rate after curative resection was 89·7 per cent. During a median follow-up of 31·5 months, there were 27 recurrences (23·1 per cent) and 13 disease-specific deaths (11·1 per cent) among the 117 patients who had an R0 resection. All patients who underwent repeat operations were alive without additional recurrence after a mean(s.d.) follow-up of 27·1(18·0) months. Conclusion: Curative surgery should be performed for control of primary NF-PNETs. Lymph node dissection for NF-PNETs of 2·5 cm or larger and at least node sampling for tumours with a diameter of 1 cm or more are recommended. Debulking surgery should be considered for advanced tumours. Paper accepted 21 June 2012 Published online in Wiley Online Library (www.bjs.co.uk). DOI: 10.1002/bjs.8892 Introduction Pancreatic neuroendocrine tumours (PNETs) are a heterogeneous group of neoplasms with diverse clinical findings considered as low-grade malignancies with a favourable prognosis. They can be functioning or non- functioning PNETs (NF-PNETs) 1 . Small tumours are readily curable by surgical resection but, unlike those with functioning PNETs, patients with NF-PNETs usually present at an advanced stage with a large mass, local invasion and distant metastases 2,3 . The annual incidence of NF-PNETs seems to be increasing, reflecting improved recognition and availability of high-quality imaging techniques 4 . For this reason, the proportion of small NF-PNETs is increasing. Several different histological classification systems have been proposed. In 2004, the World Health Organization (WHO) classified PNETs into three groups: well differentiated neuroendocrine tumour (WD-T), well differentiated neuroendocrine carcinoma (WD-C) and poorly differentiated neuroendocrine carcinoma (PD-C) 5 . The newly proposed 2010 WHO classification system is based on the European Neuroendocrine Tumor Society’s proposal to grade gastroenteropancreatic neuroendocrine tumours using mitotic rate and Ki-67 labelling index 6 . As the two WHO classifications use different parameters, the 2010 WHO classification is considered to be an additional version based on the tumour grading system rather than an entirely new version. General features of prognostic significance include tumour size, vascular invasion, mitotic rate, proliferation index, and nodal and distant metastases 7 . Complete surgical resection of these tumours has been suggested as the only potentially curative treatment. In general, aggressive surgery is recommended for localized  2012 British Journal of Surgery Society Ltd British Journal of Surgery 2012; 99: 1562–1568 Published by John Wiley & Sons Ltd