Light microscopic, immunohistochemical, and ultrastructural features of an unusual polypoid tumor of endocervix are reported. Numerous polypeptide hormone and amine-producing endocrine cells were disclosed. Main conventional characteristics were the architectural growth pattern, with infolding glands giving rise to small secondary glands, the hypermucinous benign-appearing epithelium of endocervical type, and, possibly, the stromal smooth muscle. Ultrastructural analysis showed a highly differentiated tumor. Glandular elements were surrounded by a basal lamina. Mucinous cells, several endocrine cell types, amphicrine cells, nonsecretory ciliated cells, ciliated mucinous cells, and possible reserve cells were observed. This tumor departs appreciably from normal mucosa and common varieties of endocervical polyp, particularly its distinctive endocrine profile. The present case does not correspond to a well-defined type of endocervical neoplasia. It shares morphologic analogies with mucinous tumor of ovary. The malignant potential of this lesion as well as its relationship with minimal deviation adenocarcinoma remain questionable.