Surgical technique, outcome, complications, and recurrence rate for removal of extensive perianal melanomas: 50 treated horses.

Abstract

Objective: To describe surgical treatment and outcome for horses with extensive perianal melanomas.

Animals: Gray horses treated surgically for extensive perianal melanoma between July 1, 2020, and July 31, 2023, were eligible. Horses without the entire perianal skin covered with coalescing or ulcerating melanomas were excluded.

Clinical presentation: 59 horses (30 mares, 27 geldings, and 2 stallions) met the inclusion criteria. Median age was 16 years (range, 7 to 28 years). Clinical signs included tenesmus (n = 53), weight loss (3), and hind limb lameness (1). Six horses presented with no complaints; in these horses, surgery was performed preventively. Time since melanoma first appeared was < 5 years (n = 21), 5 to 10 years (18), > 10 years (9), or unknown (11). Tails were affected in all horses. Melanoma occurred elsewhere for 58 horses. All horses underwent presurgical thoracic and abdominal ultrasonography.

Results: Horses underwent standing sedation combined with epidural anesthesia (n = 51) or general anesthesia (8). Surgery involved circumferential incisions at the junction between the skin and melanomas and mucocutaneous junction of the rectum, blunt and sharp dissection to remove the masses, and rectal reconstruction. Perirectal tumors were removed via separate vertical incisions. Tail amputation was performed for 13 horses. Follow-up data (median, 19 months; range, 6 to 48 months) were available for 50 horses; clinical signs improved for 44 (88%), recurrence was observed for 6 (12%), and complications occurred for 15 (30%).

Clinical relevance: Results indicated that this surgical procedure is a viable treatment option for horses with extensive perianal melanoma.