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 4/16/2019
Updated by: Michael Lehrer, MD, Clinical Associate Professor, Department of Dermatology, University of Pennsylvania Medical Center, Philadelphia, PA. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.