Subungual Keratoacanthoma

Supported by the Savannah and Barry French Poodle Memorial Fund
University of Pennsylvania School of Veterinary Medicine
Last Modified: August 21, 2005

Michael H. Goldschmidt, MSc, BVMS, MRCVS, Diplomate ACVP Professor and Head, Laboratory of Pathology and Toxicology Chief, Surgical Pathology Department of Pathobiology
Frances S. Shofer, PhD, Adjunct Associate Professor of Epidemiology and Biostatistics

Definition: A benign neoplasm of the nailbed epithelium.

Synonym: nailbed keratoacanthoma


Sex N Percent
Female 19 14% (21%)
Female Spayed 46 35% (33%)
Male 33 25% (25%)
Male Castrated 35 21% (21%)
(Normal Population %)


Site Percent
Forelimb 59%
Hindlimb 41%

OncoLink Veterinary Cancer Resources


  • May cause lysis of the phalangeal bone
  • Symmetrical, unencapsulated tumor with irregular scalloped borders 
  • Central core of keratin
  • Wall of the tumor composed of sheets of keratinocytes that have an abundant pale eosinophilic cytoplasm with distinct borders and large vesicular nuclei
  • There is no granular layer
  • Central aggregates of keratin are often parakeratotic 
  • Variable number of apoptotic keratinocytes may be found


  • Goldschmidt, M.H., & Hendrick, M.J. (2002). Tumors of the skin and soft tissue. In D.J. Meuten (Ed.), Tumors in domestic animals 4 th ed (pp. 45-119). Iowa: Iowa State Press
  • Goldschmidt, M.H., & Shofer, F.S. (1998). Skin tumors of the dog and cat. Woburn, MA: Butterworth-Heinemann
  • Gross, T.L., Ihrke, P.J., & Walder, E.J. (1992). Veterinary dermatopathology: A macroscopic and microscopic evaluation of canine and feline skin disease. (pp. 327-485). St. Louis, Missouri: Mosby Year Book
  • World Health Organization (1998). Histological classification of epithelial and melanocytic tumors of the skin of domestic animals (2 nd series, vol 3). Washington, DC: Armed Forces Institute of Pathology
  • Yager, J.A. & Wilcock, B.P. (1994). Color atlas and text of surgical pathology of the dog and cat. Ontario, Canada: Mosby Year Book