Ultrastructural characteristics of duodenal somatostatinomas. I. Somatostatinoma cells and Schwann-like cells.

This report describes the general ultrastructural characteristics of somatostatinoma cells and Schwann-like cells in two cases of duodenal somatostatinomas. Duodenal somatostatinoma cells had common findings to endodermal cells, i.e. the granules of exocrine type, intracytoplasmic canaliculi, microvilli, small clear vesicles and others. This may suggest that endocrine cells of the gut are of endodermal origin. On the other hand, a few Schwann-like cells were discovered in the tumor nests. Schwann-like cells surrounding the nest of tumor cells were characterized by multilayered piled up cytoplasm, abundant microfilaments and others. This fact suggests that somatostatinoma has some relationship to the nerve.