Squamous carcinoma of the endometrium with ultrastructural observations and review of the literature

Epithelial malignancies of the endometrium are almost always adenocarcinomas. Up to 50%, though, contain foci of benign or malignant squamous epithelium; but a primary malignancy with only squamous differentiation is extremely rare. We present the 17th case with, for the first time, ultrastructural observation. The tumor, confined to the fundus, was composed of sheets of squamous cells with focal pearl formation. Ultrastructural examination of the curettings revealed tonofilaments and keratohyaline granules characteristic of squamous cells, but failed to reveal attempts at luminae or acinar formation, or microvilli. The literature to date is reviewed with comments on prognosis, treatment, and histogenesis.