The significance of endocrine cells observed in ordinary carcinomas of the stomach: some considerations of the concept of atypical carcinoids evaluated at light microscopic and ultrastructural levels

Abstract

Seven cases of gastric carcinoma containing a considerable number of Grimelius-reactive argyrophil cells without typical carcinoid structures, and some with composite patterns, were examined histochemically, immunohistochemically, and ultrastructurally. For the ultrastructural study, every specimen was cut from paraffinembedded blocks of each case and reprepared after deparaffinization (the “modosi” procedure). Light microscopic observation of most specimens stained by hematoxylin and eosin exhibited the features of ordinary carcinomas. The frequency of silver-positive or immunoreactive cells differed in locations within a tumor or in individual tumors. Ultrastructurally, however, endocrine cells possessing secretory granules were observed even in silver-negative areas and were more numerous than silver-positive cells in many areas examined. The endocrine cells, therefore, might exist more frequently in gastric carcinomas than those demonstrated simply by silver stains, and such tumors might be classified as “atypical carcinoids” on the basis of ultrastructural evidence, forming a group intermediate between typical (classical) carcinoids and ordinary carcinomas.