Introduction:
Insulinomas are rare functioning neuroendocrine (NEN) tumors with an annual incidence of 1-4 cases per million. Up to 10% of insulinomas are associated with multiple endocrine neoplasia 1 (MEN1). Most of the tumors present with symptomatic hypoglycemia and the diagnosis is established by demonstrating endogenous hyperinsulinemia in the presence of hypoglycemia(1). Several non-invasive techniques are used to localize the lesion and include an ultrasound (US) abdomen, CT scan, MRI, and molecular imaging techniques like NM 18F-DOPA whole-body PET CT and Ga-68 DOTATATE scan(2-4). Due to the low sensitivity of the non-invasive methods, the localization of the tumor presents a diagnostic challenge, and invasive techniques like endoscopic ultrasound (EUS) and angiography and arterial stimulation venous sampling (ASVS) should be used if the suspicion is high(5, 6). We present a case of insulinoma presenting with seizure episodes. Laboratory testing revealed evidence of hyperglycemia, but all the non-invasive testing, including molecular imaging, was negative, and the diagnosis was established after localizing and fine-needle aspiration (FNA) of the tumor with EUS