Pancreatic endocrine tumours: histological, immuncytochemical and electronmicroscopical investigations.

Fifteen endocrine pancreatic tumours (8 insulinomas, 3 gastrinomas, 1 vipoma, 3 tumours without hormonal activity) and two cases with dysplasia of the endocrine pancreas are reported. Immunohistochemical and electronmicroscopical investigations produced evidence of multihormonality in adenomas that clinically appeared to be monohormonal. The S-phase fraction of such tumours is below 1% which indicates their low proliferative potential. The malignancy of endocrine pancreatic tumours cannot be seen from cytochemical or histological symptoms; it can be established with certainty only from the presence of metastases. Multiple endocrine adenomas should suggest the possibility of hereditary endocrine polyadenomatosis. Hyperplasia and distribution disorder of the endocrine tissue as well as pathologically increased nesidioblastic activity represent the morphologic substrate of dysplasia of the endocrine pancreas as a potential cause of hyperinsulinaemic hypoglycaemia in infancy.