Malignant melanomas in farm animals

Malignant melanomas in 5 horses, 1 calf, 1 cow and 2 pigs were described. The disease, in white or gray horses, was tegumentally located and generalized in the organs of the abdominal cavity. Microscopically, dendritic and fusiform pigment cells and multinucleated cells were identified. In the hypophysis there microcysts and in one case a hypophyseal adenoma were encountered. Electronmicroscopically, differentiated melanophores and melanophages were also found. The mature melanosomes were intensely black and the elementary granules concentrically and lamellarly arranged. In cattle, the generalized visceral malignant melanomas were described in one calf and one cow, the latter presenting cerebral localizations, too. In swine, the malignant melanomas were observed in a Duroc with visceral generalization and in a Bazna with cutaneous localization.