Mucinous metaplasia of the endometrium: ultrastructural and histochemical characteristics.

The histologic, ultrastructural, and histochemical characteristics of a focus of mucinous metaplasia in the endometrium of a postmenopausal woman are described and compared with normal endocervical and endometrial epithelium. While, architecturally, the simple coiled metaplastic glands resembled endometrial glands, cytologically, they resembled endocervical cells in the ultrastructural appearance of the mucin, as well as in the histochemical-staining properties of the intracellular secretory product. The location of the focal area of metaplasia in the fundus, apparently isolated from endocervical mucosa, as well as its architectural resemblance to endometrium, indicates that it originates from endometrium rather than endocervix.