Late-Diagnosed Insulinoma Revealed by Recurrent Hypoglycemia: A Case Report

Abstract

Insulinoma is the most common functioning neuroendocrine tumour of the pancreas, yet it remains rare, with an incidence below 5 cases per million per year. Its diagnosis is frequently delayed because of misleading, non-specific symptoms dominated by neuroglycopenic features that are often mistaken for neurological or psychiatric disorders. We report the case of a 60-year-old man with a three-year history of recurrent hypoglycaemia whose loss-of-consciousness episodes were initially interpreted as epileptic seizures and wrongly treated with antiepileptic drugs, and in whom the diagnosis of insulinoma was eventually established on documented inappropriate endogenous hyperinsulinism concomitant with hypoglycaemia, and supported by a suggestive pancreatic MRI. The patient underwent surgical enucleation of a 1.5 cm tumour of the pancreatic body; definitive histopathology confirmed a grade 2 (G2) well-differentiated neuroendocrine tumour, with immunohistochemical expression of synaptophysin and chromogranin A and a Ki-67 index of 3%. This case highlights the typical diagnostic delay of this tumour and the need to consider insulinoma in any non-diabetic adult presenting with organic hypoglycaemia.