Cystic glucagonoma with loss of heterozygosity on chromosome 11 in multiple endocrine neoplasia type 1

A 52-year-old man with a past history of a pituitary adenoma and hyperparathyroidism due to a parathyroid adenoma was admitted because of a solitary tumour of the pancreas revealed by ultrasonography. His family history was unremarkable. Plasma glucagon levels were slightly elevated (280 ng/l, normal range, 40-180 ng/l) with decreased plasma amino acid levels. Plasma glucagon levels disclosed an exaggerated response during an arginine infusion test and paradoxical elevation during a 75 g oral glucose tolerance test. Endoscopic ultrasonography revealed a monolocular cystic mass of about 3 cm in diameter in the body of the pancreas. A pancreatic tumour was diagnosed before surgery as a cystic glucagonoma. Intra-operative ultrasonography showed one cystic mass in the body of pancreas and two other solid tumours, about 1 cm and 0.5 cm in diameter, in the tail of the pancreas. Histologically, all three tumours showed neoplastic epithelial cells with round nuclei forming cords and/or a ribbon-like arrangement. They showed positive staining for Grimelius' silver stain and immunopositive cells for glucagon. Genetic analysis of the main cystic tumour revealed loss of heterozygosity (LOH) on chromosome 11. After the operation, the responses of plasma glucagon to arginine infusion and oral glucose became normal. Here we describe the usefulness of these provocation tests for early diagnosis and post-operative follow-up in a rare cystic glucagonoma associated with multiple endocrine neoplasia type 1 (MEN 1) which had LOH on chromosome 11.