For insulinomas, which generally have a more favorable prognosis than other functioning PanNETs, there is no consensus among the guidelines with regard to the need for clinical or radiological follow-up after surgery: the ENETS guideline states that patients with an insulinoma lower than grade 3 (i.e., mitotic rate < 20% mitoses per 2mm2or Ki-67 proliferation index < 20%) without signs of malignancy only need a single follow-up after 3–6 months [6, 7]. This evidence concerns the gene MKI67 and pancreatic insulinoma.