Melanoma in Grey Horses: Long-Term Welfare Management

Melanoma affects the majority of grey horses, and understanding the natural history and management options supports long-term equine welfare.

Key Facts

Over 80% of grey horses over 15 years of age develop melanoma
Tumors most commonly occur around the perineum, tail head, and parotid salivary gland area
Most equine melanomas are slow-growing and may not cause clinical problems for years
Rapidly growing or internally metastasizing tumors can cause serious welfare problems
Cisplatin intralesional injection and electrochemotherapy are established treatment options
Cimetidine has been used but evidence for efficacy is limited
Regular monitoring of tumor size, number, and site is the cornerstone of management

Welfare Considerations

Most grey horses live comfortably with melanomas for many years without significant welfare impact. The welfare concern arises when tumors impinge on functional anatomy - tumors around the anus, vulva, or rectum can cause defecation or parturition difficulties; large parotid tumors may affect swallowing. Proactive monitoring identifies the transition from benign indolent disease to problematic growth. Early intervention when tumors begin affecting function preserves welfare and extends comfortable life.

What You Can Do

Photograph and measure melanoma lesions twice yearly to track growth rate
Seek veterinary assessment if tumors begin growing rapidly or affecting functional anatomy
Discuss treatment options with a vet experienced in equine oncology for progressive lesions
Monitor perineal melanomas carefully for interference with defecation or breeding
Include melanoma assessment in routine annual veterinary health examinations