RESUMEN
Insulinoma is a rare tumor, occurring more often in women and in the older age range. Eighty percent of patients have a single benign tumor, usually 2 cm in diameter, located with about equal frequency in body, head or tail of pancreas and amenable to surgical cure. About 10% have multiple tumors. The remaining 10% of patients have metastatic malignant insulinoma. The symptom of insulinoma is characterized by the periodic attack of hypoglycemia of blood sugar level below 50mg%, by fasting or exertion, and rapid relief of symptom by oral or intravenous administration of glucose. Symptom often lead to misdiagnosis as a neurologic or psychiatric disorder. A case described by authors was 44-year old female with the chief complaints of the loss of consciousness, epileptic seizure although she has been treated by anticonvulsants. Serum blood sugar and insulin level during fasting suggested insulinoma but abdominal computed tomography shows no definitive mass in pancreas. Celiac angiography revealed insulinoma. She transferred to the department of General Surgery and was performed enucleation. Microscopic findings shows the islet cell tumor of pancreas. A brief review of the literature was made.