The spectrum and extent of islet cell histopathological findings in patients with multiple endocrine neoplasia, type I (MEN I) syndrome has never been clearly defined. Although some patients have discreet tumors causing clinically evident syndromes, others may have no symptoms until metastatic islet cell carcinoma is apparent. Whether diffuse islet cell disease occurs in all patients with grossly apparent tumors is not known. This study is an attempt to define both the functional and anatomical extent of islet cell disease and its relationship with the clinical course of patients with MEN I syndrome. The resected specimens of pancreas from 14 patients with MEN I syndrome were evaluated for hyperplasia, nesidioblastosis, multiple tumors, and evidence of malignancy. In 12 cases, specimens consisted of distal pancreas and, in 2 cases, the entire pancreas was available. Multiple sections were taken from each specimen. Immunoperoxidase staining was done for gastrin, pancreatic polypeptide, glucagon, serotonin, VIP, somatostatin, and neuron-specific enolase in sections of 24 tumors from 10 patients. Five of the 10 patients with Zollinger-Ellison syndrome underwent total gastrectomy and 3 others underwent only pancreatic procedures to control their acid hypersecretion. The following is concluded. All MEN I patients with pancreatic neoplasms have diffuse islet cell involvement consisting of nesidioblastosis, micro- and macronodular hyperplasia. Some tumors produce multiple hormones and these patients are at risk to develop new tumors, but complete excision of grossly apparent tumors may result in long-term control of the endocrinopathy present. This is particularly true for patients with insulinoma and hypoglycemia. Selected patients with gastrinoma may also be considered for excision of their islet cell tumor(s) without concomitant gastrectomy, especially if transhepatic venous sampling demonstrates a single site of excess gastrin production. However, if transhepatic venous sampling demonstrates diffuse sources of hypergastrinemia, a local pancreatic procedure will invariably be unsuccessful. Total pancreatectomy in MEN I patients with disease localized to the pancreas is the only curative surgical procedure but is rarely indicated.
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