Minimally Invasive Resection of Occult Insulinomas-Experience from an ENETS Centre of Excellence and Review of the Literature.

Abstract

<b>Background/Objectives</b>: Insulinomas are rare insulin-secreting pancreatic neuroendocrine tumours (pNETs). Preoperative tumour localisation can usually be achieved by computed tomography (CT), magnetic resonance imaging, or positron emission tomography (PET)-CT. However, cross-sectional imaging can be negative, defining an insulinoma as occult and thus hampering surgical resection. <b>Methods</b>: All patients who underwent minimally invasive (MI) surgery for an insulinoma at the University Medical Center Hamburg-Eppendorf since 2017 were analysed. Clinicopathological parameters and diagnostic and operative approaches were assessed. A literature search of the MI resection of occult insulinomas was conducted. <b>Results</b>: Of eight patients with MI-resected insulinomas, two (25%) had negative preoperative imaging. Mean tumour size was 17.2 ± 13.3 mm. Patients underwent distal pancreatectomy (DP), enucleation, and pancreatic head resection (PHR) in 62.5% (5/8), 25.0% (2/8), and 12.5% (1/8) of cases, respectively. One patient had a major postoperative complication (Clavien-Dindo ≥ 3a). Twenty-four studies reporting on 140 occult insulinomas were identified. Occult insulinomas were more frequent in females, often located in the distal pancreas and G1-differentiated. Glucagon-Like Peptide-1 Receptor/PET-CT most frequently localised the conventionally non-visible insulinomas (positive in 67/76, 88.2%). Enucleation, DP, PHR and other resections were conducted in 47/94 (50.0%), 40/94 (42.6%), 4/94 (4.3%), and 3 (3.2%) of the reported cases. MI resection was reported in 10 of 19 (52.6%) specified resections. <b>Conclusions</b>: Insulinomas can be undetectable in cross-sectional and functional imaging. Surgical exploration with intraoperative ultrasound should be considered when clinical presentation and biochemical findings are highly suggestive for insulinoma. Minimally invasive and parenchyma sparing resection is feasible even for occult insulinomas and should always be considered.