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Equine veterinary journal2026; doi: 10.1002/evj.70158

Spontaneous regression of equine sarcoids is an exceptional event.

Abstract: Sarcoids are benign, yet locally aggressive skin tumours that commonly affect horses and other equid species. The lesions are induced by bovine papillomavirus types 1, 2, and probably 13 in conjunction with other factors including trauma and a genetic predisposition. Although sarcoids have a substantial impact on the health and welfare of affected equids, information on the immune response to bovine papillomavirus infection and resulting sarcoids is limited. However, there is evidence that sarcoid disease is associated with an impaired immune response to bovine papillomavirus infection. This observation agrees with the common perception of sarcoids as persistent lesions. Contrary to this general view, there are reports on the spontaneous regression of skin tumours diagnosed as sarcoids, giving rise to the question whether sarcoids can self-resolve, and if so, under which circumstances. This review addresses this unresolved issue.
© 2026 The Author(s). Equine Veterinary Journal published by John Wiley & Sons Ltd on behalf of EVJ Ltd.
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Publication Date: 2026-03-11 PubMed ID: 41814482DOI: 10.1002/evj.70158Google Scholar: Lookup
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Summary

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Spontaneous regression of equine sarcoids, typically persistent skin tumors caused by bovine papillomavirus, is a rare occurrence. This review explores the conditions under which these tumors might self-resolve despite their usual persistence.

Overview of Equine Sarcoids

  • Equine sarcoids are benign but locally aggressive skin tumors primarily affecting horses and other equids.
  • The tumors are caused by infection with bovine papillomavirus (BPV) types 1, 2, and possibly 13.
  • Other contributing factors to sarcoid development include trauma and genetic susceptibility in the host animal.
  • Despite being benign, sarcoids can severely impact the health and welfare of the affected equids because of their growth and local invasiveness.

Immune Response to Bovine Papillomavirus and Sarcoids

  • Information about how the equine immune system responds to BPV infection and sarcoid formation is limited.
  • Evidence suggests that sarcoid disease is linked to an impaired immune response against the BPV infection.
  • This impaired immunity aligns with the common experience that sarcoids tend to persist rather than resolve spontaneously.

Spontaneous Regression of Sarcoids

  • Occasionally, sarcoids have been reported to undergo spontaneous regression, meaning they shrink or disappear without treatment.
  • Such cases are considered exceptional and are not the typical clinical presentation.
  • This phenomenon raises important questions about the biological mechanisms that might enable sarcoids to self-resolve.
  • The review explores under what circumstances spontaneous regression might occur, challenging the prevailing notion that sarcoids are invariably persistent.

Significance of the Review

  • Understanding spontaneous regression could provide insights into immune mechanisms that control or eliminate BPV infection and sarcoids.
  • This knowledge might contribute to developing better therapeutic approaches or preventive measures for sarcoids in horses.
  • The review calls attention to an unresolved issue in equine veterinary medicine and encourages further research on the immune response and tumor biology of sarcoids.

Cite This Article

APA
Brandt S. (2026). Spontaneous regression of equine sarcoids is an exceptional event. Equine Vet J. https://doi.org/10.1002/evj.70158

Publication

Equine veterinary journal
ISSN: 2042-3306
NlmUniqueID: 0173320
Country: United States
Language: English

Researcher Affiliations

Brandt, Sabine
  • Research Group Oncology, Centre of Equine Health and Research, Veterinary University, Vienna, Austria.

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