Giant insulinoma: a report of 3 cases and review of the literature.

Insulinoma is a rare pancreatic neuroendocrine tumor that is usually described as benign, sporadic, and very small (<2 cm). However, there have been rare case reports of insulinoma presenting as a giant tumor. We describe 3 cases of giant insulinomas, all of which developed liver metastases. The patients were aged 38, 63, and 67 years. Clinically, all patients presented with Whipple's triad associated with a large mass located in the pancreatic tail. The tumors ranged in size from 10 to 15 cm. On microscopic examination, the tumors were well differentiated with amyloid deposition ranging between 20% and 30%. Immunohistochemically, all 3 tumors showed strong diffuse expression of chromogranin and synaptophysin, whereas they were only focally positive for insulin. One patient developed liver recurrence 3 years after resection of the primary tumor yet remained asymptomatic without treatment. Another patient with liver recurrence underwent right hepatectomy and has been free of disease for 2 years. The third patient died of metastatic disease 13 years after initial surgery. Giant insulinomas are characterized by focal expression of insulin and high rates of liver metastases. Long-term follow-up is mandatory in these patients, as recurrence is expected after primary surgery.