Foot Superficial Spreading Malignant Melanoma in a Bay Horse. Clinical, pathological, and Long -- term follow -- up findings.

This paper describes the clinicopathological features, treatment and 22-month follow-up of a melanoma involving the coronary band and hoof wall lamellae in a 12-year-old bay Andalusian gelding. The horse exhibited a mild right forelimb lameness and history of recurrent lameness and abscessation for an ongoing 10-month period. Based on clinical and radiological examination, a keratoma at the dorsolateral aspect of the hoof, as well as a plaque-like pigmented lesion at the coronary band were diagnosed. Both lesions were removed. Microscopically, a melanoma with dermo-epidermal activity (resembling superficial spreading melanoma), was diagnosed. Further diagnostic imaging techniques showed no involvement of the surrounding structures beyond the superficial dermis. Therefore, a surgical removal of the mass, with a partial hoof wall resection was performed, and local cisplatin chemotherapy was administered. After partial regression at 6 months, the control biopsies at 12, 18 and 22 months confirmed the persistence of tumour nests with dermo – epidermal growth pattern without further invasion of deep structures or metastasis.