Goblet cell carcinoid of appendix: ultrastructural features and histogenetic aspects.

Light and electron microscopic examination of a goblet cell carcinoid revealed cells with pleomorphic neurosecretory-type granules, cells containing mucin some of which also contained these granules and less differentiated cells lacking the aforementioned features. Recent embryologic and anatomic studies of developing avian and mammalian gut, respectively, show that intestinal APUD cells are probably of endodermal origin. Therefore, mixed carcinoid tumors such as the goblet cell variant could arise in crypt base stem cells.