HPV-related follicular cysts.

Five examples of follicular cysts with papillary projections protruding into the lumen are given. In all cases, the lining was epidermoid. The cystic cavity contained compact, eosinophilic keratinous material. Groups of vacuolated keratinocytes with overlying tiers of parakeratotic cells were seen on the top of the crests. In the intervening valleys, there were irregular clumps of keratohyaline granules. These changes are diagnostic cytopathogenic effects of viral papillomas. However, papillomavirus common antigens were not identified by immunohistochemistry.