equis - Articles
Skin: neoplasia – melanoma
Synonym(s): Gray's disease
Introduction
- A common tumor of the melanotic tissue, seen most often in gray horses over 6 years old.
- Cause: unknown.
- Signs: hyperpigmented, firm nodular lesions.
- Diagnosis: pathology.
- Treatment: depends upon extent and site of lesion.
- Prognosis: variable, often benign and cause no problems (especially in gray horses); may be malignant and metastasize. As lesions enlarge they may cause problems due to obstruction of the rectum or urethra, and secondary complications such as ulceration, abscessation and maggot infestation are also seen.
Presenting signs
- Usually obvious hyperpigmented, firm nodules found on the perineum, pinnae, periocular and parotid regions of adult to old horses.
- Tumor may ulcerate.
- Horse may present with signs relating to site of tumor, eg difficulty in defecating.
- A tumor which increases in size over time.
Geographic incidence
- Worldwide.
Age predisposition
- Over 6 years old.
Breed/Species predisposition
- Other 'colored' horses tend to have single tumors more frequently located on body wall, skin and legs.
- Arabians Arab.
- Lipizzaners Lipizzaner.
- Percherons Percheron.
- Gray horses more frequently affected.
Pathogenesis
Predisposing factors
General
- Some mare families are predisposed to tumor.
Pathophysiology
- Melanosarcoma found in the same locations as melanoma, but more aggressively invasive.
- Tumors of varying malignancy arising from the melanocytes or melanoblasts of the equine skin.
- Benign or malignant, or may suddenly become malignant and metastasize widely.
Timecourse
- Variable.
Diagnosis
Subscribe To View
This article is available to subscribers.
Try a free trial today or contact us for more information.
Treatment
Subscribe To View
This article is available to subscribers.
Try a free trial today or contact us for more information.
Prevention
Subscribe To View
This article is available to subscribers.
Try a free trial today or contact us for more information.
Outcomes
Subscribe To View
This article is available to subscribers.
Try a free trial today or contact us for more information.
Further Reading
Publications
Refereed papers
- Recent references from PubMed and VetMedResource.
- Valentine B A, Calderwood Mays M B & Cheramie H S (2014) Anaplastic malignant melanoma of the tail in non-grey horses. Equine Vet Educ 26 (3), 156-158 VetMedResource.
- Moore J S et al (2013) Melanoma in horses: Current perspectives. Equine Vet Educ 25 (3), 144-151 VetMedResource.
- Barrelet A, Foote A & Littlewood J D (2010) Common equine skin tumours. UK Vet 15 (6), 9-17 VetMedResource.
- Finocchiaro L M E, Riveros M D & Gilkin G C (2009) Cytokine-enhanced vaccine and suicide gene therapy as adjuvant treatments of metastatic melanoma in a horse. Vet Rec 164 (9), 278-279 PubMed.
- Pilsworth R C & Knottenbelt D (2006) Melanoma. Equine Vet Educ 18 (5), 228-230 VetMedResource.
- Henson F M D & Dobson J M (2004) Use of radiation therapy in the treatment of equine neoplasia. Equine Vet Educ 16 (6), 315-318 VetMedResource.
- Quinn C (2003) Skin tumours in the horse: clinical presentation and management. In Pract 25 (8), 476-483 VetMedResource.
- Fleury C et al (2000) The study of cutaneous melanomas in Camargue-type gray-skinned horses (2) - epidemiological survey. Pigment Cell Res 13 (1), 47-51 PubMed.
Other sources of information
- Knottenbelt D C, Patterson-Kane J C & Snalune K L (2015) Clinical Equine Oncology. Elsevier, UK.
- Phillips J (1997) Melanoma. In: Current Therapy in Equine Medicine. 7th edn. Eds: Robinson N E & Sprayberry K A. Elsevier-Saunders, USA. pp 524-527.