This person has a wart (verruca) that has built up a cutaneous horn which is made up of hard keratin. This does not slough-off like normal skin cells.
Review Date 6/19/2021
Updated by: Ramin Fathi, MD, FAAD, Director, Phoenix Surgical Dermatology Group, Phoenix, AZ. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.