The Veterinary clinics of North America. Equine practice2019; 35(2); 311-325; doi: 10.1016/j.cveq.2019.04.003

Treatment Options for Melanoma of Gray Horses.

Abstract: All gray horses inherited a single gene mutation, STX17, that unbalances melanocyte behavior to cause graying and propensities to develop vitiligo and melanoma. The coat color genes ASIP and MC1R add risk such that relative likelihood of melanoma based on pregraying coat color is black > bay > chestnut. Melanomas begin at about 4 years. Locoregional control of melanoma masses depends on surgical removal and/or intralesional chemotherapy (possibly with adjunctive hyperthermia or electroporation). Systemic treatment is not evidence based but immunomodulators (cimetidine, levamisole) and vaccines can be tried.
Publication Date: 2019-07-08 PubMed ID: 31279435DOI: 10.1016/j.cveq.2019.04.003Google Scholar: Lookup
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The research article delves into the various treatment options for melanoma in gray horses, tracing the condition’s likelihood back to a combination of genetic factors and outlining potential management and therapeutic strategies, including surgery, chemotherapy, the application of heat or electroporation, and the use of immunomodulators and vaccines.

Genetic Determinants of Melanoma in Gray Horses

  • The research identifies a single gene mutation, STX17, as causing unbalanced melanocyte behavior in all gray horses. This imbalance results in graying and increases the propensity of the horses to develop vitiligo and melanoma.
  • Further, the coat color genes ASIP and MC1R increase the risk of melanoma. The risk profile based on pre-graying coat color is highest in black horses, followed by bay and chestnut horses.
  • The onset of melanomas typically begins when the horses are about 4 years old.

Treatment Options for Melanoma in Horses

  • Control of melanoma masses at the locoregional level primarily involves surgical removal. Intralesional chemotherapy, possibly combined with adjunctive hyperthermia or electroporation, can also be effective.
  • Systemic treatment is not yet supported by clear evidence. However, certain immunomodulators, such as cimetidine and levamisole, can be used. Another option is the trial of vaccines.

Implications of the Research

  • This study elucidates the complex genetic factors contributing to the development of melanoma in gray horses. By shedding light on specific gene mutations, the research could pave the way for advancements in genetic screening and potentially preventative measures in the future.
  • The range of therapeutic options outlined in the study underscores the complexity of treating melanoma in horses. The support for surgery and chemotherapy, in particular, remains consistent with many human treatment strategies.
  • This study also highlights the need for more research to determine the efficacy of systemic treatments for horse melanoma, thereby identifying an area for potential future scientific investigation.

Cite This Article

MacKay RJ. (2019). Treatment Options for Melanoma of Gray Horses. Vet Clin North Am Equine Pract, 35(2), 311-325.


ISSN: 1558-4224
NlmUniqueID: 8511904
Country: United States
Language: English
Volume: 35
Issue: 2
Pages: 311-325
PII: S0749-0739(19)30024-0

Researcher Affiliations

MacKay, Robert J
  • Department of Large Animal Clinical Sciences, University of Florida, PO Box 100136, Gainesville, FL 32610, USA. Electronic address:

MeSH Terms

  • Animals
  • Hair Color / genetics
  • Horse Diseases / genetics
  • Horse Diseases / therapy
  • Horses
  • Melanoma / genetics
  • Melanoma / therapy
  • Melanoma / veterinary


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