Nonfunctioning Small (≤2 cm) Neuroendocrine Pancreatic Incidentaloma

Neuroendocrine tumors (NETs) and carcinomas account for 10-15 % of all pancreatic incidentalomas. The management of pancreatic NETs depends on tumor stage and on presence or not of hormonal syndrome. The therapeutic approach for hormonally functional tumor, or large tumor (\> 2 cm) with local, vascular or lymph nodes invasion, highly suggestive of malignancy, or in presence of metastasis, is well admitted: surgery is indicated or should be discussed. However, the attitude is less consensual for small (≤ 2 cm) non-functioning (NF) and non-metastatic lesions. In English, American or French recommendations, systematic surgical resection with lymphadenectomy is currently recommended in all medically fit patients. The follow-up (FU) is possible for tumors \<2 cm (T1) located in the pancreatic head and for which enucleation is not feasible. Several recently published retrospective studies discuss the "non- surgical" management of the small NF incidentally detected pancreatic NETs (IPNETs) and highlight the necessity of developing guidelines for management of these patients. A strict correlation between tumor size and malignancy of these tumors was demonstrated in the single-center retrospective Italian study of Bettini and col., which included all patients with NF PNETs who underwent curative (R0) resection during 18 years. In the group of 51 patients with small size of T (2 cm or less), incidentally discovered, the majority of lesion was benign, and the authors concluded that follow-up can be proposed in patients with incidentally discovered NF PNETs ≤ 2 cm. However in despite of small size and asymptomatic character of the tumor, the rate of malignancy of NF IPNETs ≤ 2 cm was estimated to be 24 % (in 18% and 6% of cases, uncertain behaviour and carcinoma were present). Given the inherent morbidities associated with pancreatic surgery, a risk-benefit calculation may favour surveillance rather than surgery in highly selected patients. Thus, a better understanding of NF IPNETs and identification of their prognostic factors can be of help to select a subgroup of patients who could benefit from a long-term surveillance rather than a systematic surgical resection. Clearly, large prospective trials are needed to validate this approach.