Intracellular and extracellular fibrillar structures in gastroduodenal endocrine tumors.

Sixteen gastroduodenal endocrine tumors have been examined ultrastructurally for the presence of intracellular and extracellular fibrillar material. Intracellular juxtanuclear fibrillar bodies, often with intermingled secretory granules, were observed in one antral, one pyloric, and three duodenal tumors. In the pyloric tumor there were also extracellular fibrillar structures, which, in contrast to the intracellular fibrils, showed a green birefringence after staining with alkaline Congo red indicating the amyloid nature of these fibrils. One endocrine tumor localized to the fundus-corpus contained extracellular fibrillar bodies of a type typical of adenoid cystic carcinoma.