A Non-cutaneous Form of Melanoma in a Goat during Meat Inspection: a Case Report

Malignant melanoma is a neoplasm that originates from melanocytes. This tumor is observed in cutaneous and non-cutaneous forms, and it is considered one of the most life-threatening types of cancers. Non-cutaneous melanoma is a complex of unique and malignant complications that are easily separable from cutaneous type. Since the ultraviolet radiation from the sun damages DNA and is an oxidative stress factor in melanoma and there are more melanocytes in the basal layer of skin than other parts of the body, the cutaneous form has more prevalence. Most of the time, non-cutaneous form is the result of cutaneous metastasis but both forms can occur primarily. Furthermore, non-cutaneous form usually happens in mucosal layers, intestines, and eyes; moreover, the main reasons are ectopic melanocytes or their unwanted regressive growing. Malignant melanoma can occur in all domestic animals; however, they seem to be rare in sheep and goats. Herein, we describe a rare case of the primary non-cutaneous form of malignant melanoma in a three-year-old indigenous female goat. During meat inspection procedures in a slaughterhouse in Tabriz, Iran, we encountered numerous round firm black masses on visceral surfaces and serous membranes of the abdominal and thoracic cavities. The liver and lungs were prominently affected. Samples were taken from involved parts, and malignant melanoma was confirmed in the histopathological examination due to pleomorphism and polymorphism and melanin pigments in cells with eosinophilic cytoplasm. According to what was stated in the "manual on meat inspection for developing countries", the carcass was not convenient for human use and condemned by the inspector.