Introduction: Malignant melanoma is common in the dog and uncommon in other domestic species. This tumor was reported in white Angora goats and grey or brown goats. The most common sites of malignant melanoma in goats are the solar-exposed areas of the ear, face, and perineum. The involvement of the coronary band area and the medial claw of the right hindfoot is reported in a crossbred goat too. Malignant melanomas invade locally and metastasize through lymphatics and blood vessels. This study describes the gross and histopathological features of a malignant melanoma. Methods: A five years old native goat due to presence of an ulcerated mass around anus was referred to Department of Pathobiology. After gross examination of the mass, surgical treatment was performed. Histopathology of the excisional biopsy revealed a large population of pleomorphic melanocytes in dermis. The tumor cells had epithelioid pattern and nuclear pleomorphism with prominent nucleoli. The amount of melanin pigment was variable in different sections. The collagenous stroma was present between the large clusters of neoplastic cells. General features of malignancies including necrosis, ulceration, infiltration of inflammatory cells, and hemorrhage were observed too. Conclusions: Based on gross and histopathological characteristics, the mass was diagnosed as poorly differentiated melanoma.

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