Equine melanomas
Melanomas in Horses: What You Need to Know
Melanomas in horses are tumors that develop from pigment-producing cells called melanocytes. They are most commonly found in gray horses, with studies showing that over 80% of gray horses older than 15 years develop some form of melanoma. These tumors usually appear as firm, dark (black or gray) lumps under the skin, often around the tail, anus, sheath, lips, or eyelids.
Are Equine Melanomas Dangerous?
In most gray horses, melanomas tend to grow slowly and may remain benign (non-cancerous) for many years.
However, in some cases, they can become malignant (cancerous), growing aggressively, spreading internally, and affecting organs like the liver, spleen, or lungs.
Non-gray horses that develop melanomas are more likely to experience faster-growing and more malignant tumors.
How Are They Different from Human Melanomas?
Human melanomas are almost always aggressive and malignant, often linked to sun exposure. Early detection and treatment are crucial because they can spread quickly.
Equine melanomas, particularly in gray horses, often start as benign growths and don’t always spread. However, if they become malignant, they can still be life-threatening.
In humans, melanomas arise more commonly on sun-exposed skin, whereas in horses, they typically appear in specific areas, especially under the tail and around the anus.
Treatment Options for Equine Melanomas
Monitoring: If the melanomas are small and not growing, your vet may recommend keeping an eye on them.
Surgical Removal: Best for small, early-stage tumors before they become too large or spread.
Cryotherapy (Freezing): Can be used to destroy small tumors.
Immunotherapy & Vaccines: Newer treatments, including a melanoma vaccine originally developed for dogs, show promise in slowing tumor growth in horses.
Cimetidine (an ulcer medication): Some studies suggest it may help slow melanoma progression, though results vary.
If your horse develops melanomas, it’s best to work closely with your veterinarian to monitor and manage them. While many gray horses live full lives with melanomas, early treatment is key if they start growing or spreading.
