An ultrastructural study of a sclerosing epithelial hamartoma

The histological and ultrastructural features of a sclerosing epithelial hamartoma are described. By electron microscopy, epithelial cords formed by basal-like cells and epithelial cysts with a pattern of keratinization similar to that of normal epidermis or of follicular infundibula were seen. By conventional light microscopy, continuities were found between the epithelial cords and the overlying epidermis. The stroma was found to be fibrous and contained some fibroblasts or possibly myofibroblasts with bundles of microfilaments. The data are interpreted with respect to the origin of the neoplasm, its line of differentiation, and its sclerosing behavior.