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Minimally Invasive Resection of Occult Insulinomas—Experience from an ENETS Centre of Excellence and Review of the Literature
by
, , , ,
Alina S. Ritter
1,†, 
Feline Ockenga
1,†,
Kira C. Steinkraus
1,
Jelte Poppinga
1,
Philipp H. von Kroge
1,
Tania Amin
2,
Fabrice Viol
2,
Thorben W. Fründt
2,
Felix Nickel
1,
Thilo Hackert
1 and
Anna Nießen
1,* 1
Department of General, Visceral and Thoracic Surgery, University Medical Center Hamburg-Eppendorf, 20246 Hamburg, Germany
2
I. Department of Medicine, University Medical Center Hamburg-Eppendorf, 20246 Hamburg, Germany
*
Author to whom correspondence should be addressed.
†
These authors contributed equally to this work.
Cancers 2025, 17(23), 3857; https://doi.org/10.3390/cancers17233857 (registering DOI)
Submission received: 21 October 2025
/
Revised: 24 November 2025
/
Accepted: 27 November 2025
/
Published: 30 November 2025
(This article belongs to the Special Issue Treatment Options and Risk Factors of Pancreatic Neuroendocrine Neoplasms)
Simple Summary
Insulinomas are rare pancreatic neuroendocrine tumours that systemically secrete insulin, resulting in severe hypoglycaemia. In some cases, insulinoma cannot be localised through radiological imaging and are thus called occult insulinomas. Surgical resection remains the only cure for insulinomas and is preferably performed minimally invasively. All insulinomas that were resected minimally invasively at the University Medical Center Hamburg-Eppendorf between 2017 and 2025 were analysed. Two of eight insulinomas could not be localised in conventional imaging, but were still successfully and safely resected with keyhole surgery. In the available literature, the minimally invasive and parenchyma-sparing resection of occult insulinomas has likewise been reported as feasible. Intraoperative ultrasound can facilitate intraoperative tumour localisation. Occult insulinomas were more frequent in females and more often localised in the distal pancreas.
Abstract
Background/Objectives: 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. Methods: 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. Results: 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. Conclusions: 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.
