COEXPRESSION OF INSULIN AND SOMATOSTATIN IN SINGLE SECRETORY GRANULESOF A PANCREATIC ENDOCRINE TUMOR

Pancreatic endocrine tumors, examined by immunohistochemistry, were fo und to be associated with multihormonal production, and recent studies , performed by employing double immunostaining methods, reported the c oexpression of hormones in single cells or in single secretory granule s. These findings have been attributed to the heterogeneity of the neo plastic cell population, characterized by the emergence of clones with different phenotypes, and were considered a sign of cell dedifferenti ation or malignancy. In this study we describe a case of pancreatic en docrine tumor that showed focal colocalization of insulin and somatost atin in single secretory granules, by means of double labelling immuno electron microscopy. We think that this observation can be linked to t he hypothesis of those authors who speculated upon the appearence of p olycrine cells in human fetal pancreas during embryogenesis.