title: Equine exuberant granulation tissue and human keloids: a comparative histopathologic study.
abstract: OBJECTIVE
  To compare histopathologic features of a fibroproliferative disorder in horses (exuberant granulation tissue-EGT) and people (keloid).
  
  
  METHODS
  Archival tissue samples of EGT (n = 8) and keloid (12).
  
  
  METHODS
  After automated hematoxylin and eosin, histochemical (Gomori trichrome, Verhoeff-van Gieson elastin) and immunohistochemical (vimentin, α-smooth muscle actin, CD34, CD68, CD117) stainings, tissue sections were evaluated using a semi-quantitative grading scale for presence or absence of ulceration, keloidal collagen, myofibroblasts, and elastic fibers as well as degree of inflammation, fibrosis, vascularity, and orientation of collagen fibers.
  
  
  RESULTS
  Superficial dermis and deep dermis of both horses and people had increased numbers of haphazardly oriented thickened collagen fibers; however, only keloids contained "keloidal" collagen. Fibroblast numbers were markedly increased in both groups but only EGT had myofibroblasts. Minimal vascularity was observed in the deep dermis of both groups. The superficial dermis in EGT was characterized by small vessels within immature granulation tissue. Macrophages and mast cells were infrequently found in both groups but polymorphonuclear cells were markedly increased in EGT.
  
  
  CONCLUSIONS
  Humans and horses are the only mammals known to naturally develop excessive granulation during wound healing; however, similarities and differences between fibroblast populations and associated collagen have not been reported. Inflammatory response may contribute to observed differences in the cellular populations, with EGT possessing markedly increased myofibroblasts, small vessels, and acute inflammatory cells compared with keloids. Further work is warranted to develop common treatment strategies for these fibroproliferative conditions.
authors.affiliation: Université de Montréal, Saint-Hyacinthe, Québec, Canada.
authors.forename: Christine L
authors.initials: CL
authors.lastname: Theoret
authors.forename: Oluyinka O
authors.initials: OO
authors.lastname: Olutoye
authors.forename: Laura K S
authors.initials: LK
authors.lastname: Parnell
authors.forename: John
authors.initials: J
authors.lastname: Hicks
mesh_terms: D000818:Animals; D017439:Cicatrix, Hypertrophic / Q000473:pathology / Q000662:veterinary*; D020405:Dermis; D004817:Epidermis; D005355:Fibrosis; D005786:Gene Expression Regulation; D006734:Horse Diseases / Q000473:pathology*; D006736:Horses; D006801:Humans; D007627:Keloid / Q000473:pathology*; D014945:Wound Healing