Dermal melanomas are extremely common in gray horses, with up to 80% of gray horses over 15 years affected. They arise from melanocytes that accumulate excessive melanin during the graying process. Initially benign but approximately 66% will eventually become malignant with metastasis to internal organs (lymph nodes, lungs, liver, spleen, guttural pouches). Non-gray horses can also develop melanomas, which tend to be more aggressive.
Firm, dark (black/brown) nodules most commonly under the tail, perianal region, parotid salivary gland area, eyelids, and commissure of lips; usually slow-growing; may ulcerate; large perineal masses can obstruct defecation; internal metastasis may cause weight loss, colic, or organ dysfunction
Dermal melanomas are extremely common in gray horses, with up to 80% of gray horses over 15 years affected. They arise from melanocytes that accumulate excessive melanin during the graying process. Initially benign but approximately 66% will eventually become malignant with metastasis to internal organs (lymph nodes, lungs, liver, spleen, guttural pouches). Non-gray horses can also develop melanomas, which tend to be more aggressive.
Firm, dark (black/brown) nodules most commonly under the tail, perianal region, parotid salivary gland area, eyelids, and commissure of lips; usually slow-growing; may ulcerate; large perineal masses can obstruct defecation; internal metastasis may cause weight loss, colic, or organ dysfunction