Melanoma in horses: distribution by sex, age, nationality, and slaughterhouse findings in 28 horses from Northern Italy

Melanomas are dermal-epidermal and subcutaneous tumors commonly found in horses, especially those with grey coats. This study aimed to characterize melanomas in slaughtered horses by analyzing their distribution according to sex, age, and nationality, and to describe the veterinary inspection interventions required at slaughterhouses based on lymph node involvement and distant metastases in a province of northern Italy. Between January and December 2024, 182 grey horses were examined, and 28 cases of melanoma were identified (15% of grey horses) with an average age of 14 years: 8 males (mean age 13 years) and 20 females (mean age 15 years). The nationalities represented were 21 French, 2 Hungarian, 2 Italian, 2 Slovenian, and 1 Polish. The most commonly affected sites were the base of the tail and perineal area (26 cases), followed by the cardiac muscle, and trachea. Nineteen cases were classified as dermal melanomas, 5 as melanocytomas, 2 as anaplastic melanomas, and 2 as noncutaneous melanomas; 2 had lymph node metastases, 14 localized lesions, and 12 distant metastases. Eighteen horses underwent tumor removal with carcass trimming, while 10 required complete carcass condemnation. This study provides information on the clinical behavior of melanomas in slaughtered horses and the interventions required for meat processing during postmortem inspection in slaughterhouses.