What should you know about melanoma in grey horses?

Grey horses commonly develop areas of dark pigment and may form firm nodules beneath the skin. Lesions are often noticed around the dock and anus, under the tail, beneath the mane, or near the eyelids, although other sites can be involved. A nodule may remain quiet for a long time, then enlarge, ulcerate, bleed, become infected, or interfere with defecation, grooming, vision, or movement. Not every dark lump is melanoma, and a veterinarian may need to examine, measure, sample, or image it.

The care plan depends on the number, size, location, growth pattern, and effect on the horse. Removing a lesion can be difficult when it lies close to the anus, tail, eye, or another structure where normal tissue is limited.

Ask your equine veterinarian to assess any new lump, a lump that changes, or a mass that rubs, cracks, or discharges. Keep a simple record of its location and appearance, and do not squeeze, cut, or apply caustic products. The veterinarian may recommend observation with scheduled measurements, biopsy, surgical excision, or tumour removal surgery. If several lesions exist or a mass cannot be removed safely, referral to an equine surgical or oncology service may help plan care.

Arrange urgent veterinary care for heavy bleeding, foul discharge, rapidly worsening swelling, fever, severe pain, difficulty passing manure, inability to see, or sudden weakness. A mass that blocks the anus, damages the eye, or causes repeated straining should not wait for a routine check. After a diagnosis, new coughing, breathing trouble, marked weight loss, or neurological changes need prompt review because serious disease may have spread.

Ask whether the lesion can be monitored safely, how it will be measured, and whether sampling could change the plan. Discuss surgical access, wound care, pain relief, effects on tail or bowel function, and signs of infection. Ask how often the horse should be rechecked and whether other nodules need mapping.