Iowa State University Veterinarian Records, RS 22/6/0/9, University Archives, Special Collections Department, Iowa State University, http://www.add.lib.iastate.edu/spcl/arch/rgrp/22-6-0-9.html
In equines the formation of exuberant granulation tissue is of common occurrence in wounds which are attended by considerable irritation. However, certain individuals have what is known as "blastoma constitution", which is a tendency to produce enormous amounts of connective tissue from comparatively slight irritation. Frequent sequelae of these exuberations are keloids, which are not true tumors but excessive formations of scar tissue.
Cornwell, G. W.
"Keloid Formation A Horse,"
Iowa State University Veterinarian: Vol. 3
, Article 17.
Available at: http://lib.dr.iastate.edu/iowastate_veterinarian/vol3/iss1/17