Original StudySquamous Cell Carcinoma Arising in Keratoacanthoma: A Neglected Phenomenon in the ElderlyWeedon, David D MD, FRCPA; Malo, Jonathan BSc (Physiol); Brooks, David B Biomed Sci; Williamson, Richard MBBS, FRCPA Author Information From the Sullivan Nicolaides Pathology, Taringa, Queensland, Australia. Reprints: Dr. David D. Weedon, MD, FRCPA, Sullivan Nicolaides Pathology, 134 Whitmore St, Taringa, Queensland 4068, Australia (e-mail: [email protected]). The American Journal of Dermatopathology: July 2010 - Volume 32 - Issue 5 - p 423-426 doi: 10.1097/DAD.0b013e3181c4340a Buy Metrics Abstract Keratoacanthoma is a unique clinicopathologic entity with a behavior and clinical outcome that differs markedly from that of squamous cell carcinoma. The development of squamous cell carcinoma in a keratoacanthoma alluded to by Rook and Whimster in 1979 and by Reed in 1993 was confirmed by Sánchez Yus et al in 2000. We found this phenomenon in 5.7% of keratoacanthomas in a series of 3465 cases. Its incidence in patients older than 90 years was 13.9%. The incidence of perineural invasion in this series of keratoacanthomas was 0.2%. Copyright © 2010 Wolters Kluwer Health, Inc. All rights reserved.