Endocrine tumors of the pancreas: the pathologist's approach.

The introduction of modern cytological techniques has provided the pathologist of tools that considerably improved his analysis of pancreatic endocrine tumors and that are discussed in this review. Hormonal characterization of the tumors by immunohistochemistry significantly contributed to the definition of the current functional classification of the tumors and proved that ectopic tumors (producing extrapancreatic hormones) are as common as entopic tumors synthesizing pancreatic hormones. The identification of neuroendocrine markers and of other active non-hormonal substances extended our knowledge on the functional properties of tumor cells often with significant fall out on the biology of the corresponding normal cells. Current studies are mostly oriented toward the analysis of cell proliferation and appear to open promising perspectives for the prognostic evaluation of the tumor course.