[18F]FB(ePEG12)12-Exendin-4 positron emission tomography/magnetic resonance imaging for precise preoperative localization of a pancreatic-head insulinoma: a case report with review of literature.

Insulinomas are rare functional pancreatic neuroendocrine tumors that cause hypoglycemia from inappropriate insulin secretion. Surgical resection is curative but hinges on accurate preoperative localization. Conventional imaging with computed tomography and magnetic resonance imaging may miss small lesions, and invasive tests such as endoscopic ultrasound tissue acquisition and the selective arterial calcium stimulation test, while informative, are operator-dependent and not invariably conclusive. Glucagon-like peptide-1 receptor-targeted positron emission tomography has emerged as a sensitive, noninvasive localization tool. A 53-year-old man presented with endogenous hyperinsulinemic hypoglycemia, including a witnessed nocturnal seizure (glucose 27 mg/dL; immunoreactive insulin 40.5 μU/mL). Cross-sectional imaging showed a 10-12 mm hypervascular tumor in the pancreatic head. Glucagon-like peptide-1 receptor imaging with [18F]FB(ePEG12)12-exendin-4 positron emission tomography/magnetic resonance imaging (PET/MRI) acquired at end-expiration demonstrated intense focal uptake confined to the lesion, with high lesion-to-pancreas contrast and no additional tumor. Consistently, the selective arterial calcium stimulation test localized secretion to the superior mesenteric artery territory. Subsequently, pancreaticoduodenectomy achieved cure and pathology confirmed a well-differentiated insulinoma (grade 1; Ki-67 <1%). He remains asymptomatic without recurrence at 24 months. [18F]FB(ePEG12)12-exendin-4 PET combined with high-contrast, motion-managed magnetic resonance imaging enabled precise, confident localization in the motion-prone subdiaphragmatic region when cytology was nondiagnostic, directly informing the operative plan. [18F]FB(ePEG12)12-exendin-4 PET/MRI is feasible and clinically informative for preoperative localization of pancreatic-head insulinoma, facilitating curative surgery. Larger series are needed to define indications relative to other imaging strategies.