Unusual [18F]FDOPA PET-CT maging of insulinomas in children

Abstract Purpose Insulinomas are rare pancreatic neuroendocrine tumours, causing recurrent episodes of hypoglycaemia. Accurate localisation is essential for surgical management, yet imaging remains challenging. This case series presents unusual findings of paediatric insulinomas on [ 18 F]-dihydroxyphenylalanine ([ 18 F]FDOPA) positron emission tomography-computed tomography (PET-CT) imaging. Methods We retrospectively reviewed medical notes and investigations of histologically proven paediatric insulinoma cases (n=4) presenting to Royal Manchester Children’s Hospital between 2008 and 2024. All patients underwent [ 18 F]FDOPA PET-CT as part of their diagnostic workup. Imaging findings were analysed, with particular attention to tracer uptake patterns. Results Contrary to the increased tracer uptake typically seen in neuroendocrine tumours, three of the four insulinomas demonstrated focal photopenia at the site of the tumour on [ 18 F]FDOPA PET-CT. Only one case showed increased uptake, suggesting a predominance of reduced, rather than enhanced, tracer activity in paediatric insulinomas Conclusion Photopenia on [ 18 F]FDOPA PET-CT may be a more frequent finding than increased uptake in paediatric insulinomas. Recognizing this atypical pattern is important for accurate tumour localisation before surgical management. Further studies are needed to validate these findings and find a mechanistic explanation.