Utility of Endoscopic Ultrasound Multimodal Examination with Fine Needle Aspiration for the Diagnosis of Pancreatic Insulinoma – A Case Report

Insulinomas are benign insulin-secreting neuroendocrine tumors originating in the pancreatic beta cells. Symptoms are caused by hypoglycemia and clinical diagnosis is based on establishing their relationship to fasting, usually via a fasting test. The most conclusive imaging tests are endoscopic ultrasound (EUS) and CT. Surgery is the treatment of choice. A 33 year old male presented with a 2-year history of hunger which had intensified in the previous 6 months with added accompanying symptoms, culminating with an acute episode - loss of consciousness and seizures - which resolved after administering i.v. glucose. A fasting test was performed, with results suggestive for an insulinoma. Dual-phase CT showed a mass in the tail of the pancreas but no contrast enhancement. EUS was used for further assessment: B-mode showed a hypoechoic focal mass with a cystic component, on contrast enhancement the pattern was hypovascular, and elastography showed soft tissue. EUS fine needle aspiration (FNA) was performed and the immunohistochemistry (IHC) assay was conclusive for a neuroendocrine tumor of the pancreas. Treatment consisted of caudal pancreatectomy, with no recurrence after 1-year follow-up. Although this case started with a classic clinical presentation of an insulinoma, imaging studies related to tumor vascularization raised doubts about the actual diagnosis. Nevertheless, multimodal EUS assessment with FNA was considered to be the most appropriate diagnostic technique for detection, characterization and staging of the mass. EUS findings together with the IHC assay were able to offer the definite diagnosis of a benign neuroendocrine tumor and allowed us to refer the patient for appropriate treatment.