Abstract

CARDONA A, José A; VARGAS V, Marlene I  and  BUITRAGO M, Jhonny A. Clinical, Histopathological and Histochemical Evaluation of Cutaneous Melanoma in Horses (Equus ferus caballus) of Córdoba Department, Colombia. Rev. Fac. Cienc. Vet. [online]. 2016, vol.57, n.1, pp.22-31. ISSN 0258-6576.

The aim of this study was to evaluate the clinical, histological, and histochemical aspects of cutaneous melanoma (CM) in convenience horses (Equus ferus caballus) of the Department of Cordoba, Colombia. The study was descriptive, non-probabilistic. A total of 24 horses from different farms, with clinical and histopathologic diagnosis of MC, were used. In describing the lesions, infiltrating or plate-appearance, firm, exophytic, pigmented, and alopecic tumor masses, were observed and; in some cases, skin ulcerations were seen. However, the adjacent tissues (bone or muscle) were not invaded by injuries. The lesions were located in the ventral surface of the tail, the perianal, perineal, and genital regions (vulva, foreskin, and penis), neck, eyelids, and labial commissures of the animals studied. Histological examination with hematoxylin staining-eosin revealed the presence of cells of variable size; similarly, the nuclei were different between cells and mitotic figures were observed. Most of the observed cell types were: epithelioid, pleomorphic, and round cells. Tumor areas were vaguely defined and highly pigmented, showing the presence of large amounts of grouped atypical melanocytes (in nests or teak). With trichrome Gomori staining, poor dermal proliferation of disorganized collagen was observed, with scarce presence of diffuse connective tissue, whereas with the polarization microscopy technique, which uses picrosirius red staining, areas of red birefringence were observed, indicating moderate presence of mature type I collagen (bright red color in polarization). The definitive diagnosis of MC was based on clinical features, differential diagnosis, and histopathologic findings. These were conclusive diagnostic methods for MC, becoming the first report of this disease in horses of the Cordoba Department, Colombia.

Keywords : CM; melanocytic; tumor; melanin; equines.

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