RESUMEN
We report a case of an insulinoma that was not identified on either Computerized Tomography (CT) scan and Magnetic Resonance Imaging (MRI). Endoscopic ultrasonography (EUS) revealed a small insulinoma located at the body of the pancreas, which was histologically confirmed. The patient underwent a laparotomy but no tumour was identified either on palpation or with intra-operative ultrasound (IOUS). Subsequently, a further EUS was performed and after the tumour was identified was injected with blue dye. The patient then underwent a second exploratory laparotomy and a tumour at the posterior aspect of the pancreas close to the left side of the portal vein was identified and was successfully excised. Histology confirmed the presence of an endocrine tumour staining for chromogranin A and insulin. The patient had an uneventful postoperative recovery and has developed no further episodes of hypoglycemia 3 years after surgery.