Giant insulinoma in a patient with multiple endocrine neoplasia-type I: a case report.

We report a case of giant cystic insulinoma constituting part of multiple endocrine neoplasia (MEN) type I. A 29-year-old Japanese man presented with a history of recurrent hypoglycemic attacks. Endocrine examination showed hyperinsulinemia discordant with hypoglycemia, and a giant cystic insulinoma (11 x 10 cm) located in the pancreatic tail was detected radiologically. Hyperprolactinemia due to pituitary adenoma and hyperparathyroidism due to parathyroid hyperplasia were also present. The insulinoma, prolactinoma and hyperplastic parathyroid gland were surgically removed. Fluorescent microsatellite analysis detected loss of heterozygosity (LOH) in chromosome 11q13 in DNA samples from all resected tissues but not from white blood cells. This is a rare case of MEN type I because of the giant cystic insulinoma and the evidence of common LOH detected in all MEN type I tissues.