The inverted follicular keratosis. A surprising variant of seborrheic wart.

The pathological features of 29 lesions that had been diagnosed as inverted follicular keratoma have been reviewed. The clinical data suggest that these lesions occur predominantly on the face of middle-aged or elderly man. None were correctly diagnosed before removal. The main histological points noted were the presence of an invaginated type of architecture, foci of keratinization (squamous eddies) and areas of basaloid cells which were arranged haphazardly with mitotic figures (Borst-Jadassohn change). All the histological features seen are also observed in irritated or traumatized seborrheic warts and no evidence was found for the original suggestion that these lesions derive from hair follicles.