Ultrastructure of endometrial stromal foam cells.

An endometrium with cystic-glandular hyperplasia contained large foam cells in the stroma. The majority had ultrastructural characteristics of endometrial stromal cells, although a few were interpreted as macrophages. Endometrial stromal cells that appeared normal by light microscopy contained varying quantities of lipid on ultrastructural examination, and differed from the predominate type of foam cell only by having less cytoplasmic volume and maintaining an elongated shape. Cells intermediate in size and shape between normal stromal cells and foam cells further substantiated the origin of most of the foam cells from endometrial stroma.