Verruciform xanthoma in an epithelial nevus.

Verruciform xanthoma is an unusual lesion that was initially reported in 1971. Clinically, it is a verrucous, vascular, epithelial plaque or papillomatous growth commonly found on oral or mucosal tissues. Histologically, it is characterized by a verruciform epithelium with abundant parakeratosis and by foam cells occupying the vascularized dermal papillae. This is the second extramucosal verruciform xanthoma reported. Our patient had several unique features. She is the youngest patient described to date, her lesion is the largest reported, and the lesion occurred in an epithelial nevus-type eruption of a phocomelic extremity. Light and electron microscopic studies disclosed abnormal keratinization, mast cell proliferation, and the previously described foam cells. We believe that the verruciform xanthoma in our patient represents part of a reaction to the epithelial nevus occurring in association with a developmental anomaly.