Hyperplastic lesions of the gastrointestinal endocrine cells.

A substantial body of knowledge is presently available on the morphologic, histochemical, ultrastructural, and functional characteristics of both the normal endocrine cell population of the gut and their related endocrine tumors. In contrast to this, we have only recently begun to recognize the existence of hyperplastic proliferations of various endocrine cell types, and information is therefore steadily accumulating on the morphologic criteria for their recognition, their clinicopathologic correlates and the clinical relevance of this morphologic finding. Hyperplastic proliferations of various endocrine cell types most often develop as a secondary phenomenon in a variety of clinical situations, and may modify the clinical course of the associated condition in a manner that underscores the functional interrelationships these endocrine cells have not only with each other but with other cell types as well. However, similar proliferations may also occur as a primary event (e.g. primary antral G-cell hyperplasia) and give rise to clinical and biochemical features attributable to the overproduction of their specific hormonal product (e.g. Zollinger-Ellison Syndrome, type I). This communication provides a broad overview of the current state of our knowledge of hyperplastic lesions of a variety of gut endocrine cell types in humans, their pathophysiologic significance, their relationship (if any) to the subsequent development of endocrine tumors (i.e. the hyperplasia-neoplasia sequence), and the utility of certain experimental models for the study of such proliferations in a variety of animal species.