Inverted variant of carcinoma cuniculatum of the toe

An inverted variant of carcinoma cuniculatum of the great toe of a 55-year-old man is reported. Clinically the tumor presented as an inflammatory process of the toe with purulent drainage and bone destruction in the absence of cutaneous ulcer or exophytic growth. It was characterized histologically by endophytic sheets and cords of well-differentiated keratinizing squamous epithelium with minimal cellular atypia and numerous intraepithelial keratin cysts and microabscesses. The diagnostic challenge of the clinical presentation of this variant is emphasized.