Neonatal islet cell adenoma: a distinct type of islet cell tumor?

An encapsulated, compact-type islet cell adenoma of the pancreas, found in a newborn infant with hyperinsulinemic hypoglycemia, was investigated by conventional histology and immunofluorescence. Although the histologic structure of the tumor was indistinguishable from that of most islet cell tumors of adults, immunofluorescence revealed that the four islet cell hormones (insulin, glucagon, somatostatin, and pancreatic polypeptide) were all present in the tumor. They were stored in different cells that showed the same spatial distribution usually seen in normal islets. We conclude that neonatal islet cell adenoma can be distinguished from those of adults on the basis of the content and topographic distribution of their constituent endocrine cells.