Verrucous cyst.

A verrucous cyst is an unusual, histopathologically distinctive, epidermoid cyst characterised by verrucous changes in its wall. We report two cases of verrucous cysts in different patients, one on the back and the other on the cheek. Clinically, the lesions were thought to represent an epidermoid cyst and a basal cell carcinoma, respectively. Histologically, we found in both cases an intradermal epidermoid cyst lined by a stratified squamous epithelium with focal cytopathogenic viral changes, consisting of papillomatosis, ortho- and parakeratosis, and hypergranulosis. One case also showed, within the squamous areas of the hyperplastic epithelium, occasional squamous eddies. These histopathological features support the diagnosis of verrucous cyst, which may represent a manifestation of human papillomavirus infection. This virus may induce cyst formation or just infect a pre-existing one.