Pancreatic lesions and hormonal profile of pancreatic tumors in multiple endocrine neoplasia type I. An immunocytochemical study of nine patients.

Pancreatic specimens of nine patients suffering from multiple endocrine neoplasia type I (MEN I) were investigated with regard to tumor frequency and growth pattern, islet hyperplasia and endocrine cell neoformation, immunocytochemical hormone profile of the tumors, and correlation to clinical symptoms. The majority of the 201 tumors were microadenomas (diameter less than 0.5 cm), which frequently displayed a trabecular growth pattern. Microadenomatosis was considered the most distinct feature of the MEN I pancreas. Additional larger tumors (diameter greater than 1.0 cm) were found in five patients. Whereas islet hyperplasia appears not to belong to the spectrum of the pancreatic lesions in MEN I, nesidioblastosis was occasionally observed. Immunocytochemical screening revealed that among hormone-positive tumors (approximately 80% of the tumors), pancreatic polypeptide tumors (PPomas), glucagonomas, and insulinomas were the most frequent. The high incidence of PPomas in these pancreases probably accounts for the elevated serum PP levels found in many MEN I patients. Somatostatinomas, gastrinomas, vasoactive intestinal polypeptide tumors (VIPomas), and neurotensinomas were rare. Clinically overt hyperinsulinism, observed in two patients and associated with a large insulinoma, was cured by tumor resection. Eight of nine patients presented a Zollinger-Ellison's syndrome (ZES), but only in two patients were gastrin-producing tumors found. The source of gastrin in MEN I patients with a ZES, in whom no gastrinoma could be detected, remains unclear.