Resumo

CHAVES VELASQUEZ, Carlos Alberto; ASTAIZA MARTINEZ, Juan Manuel; BENAVIDES MELO, Carmenza Janneth  e  VALLEJO TIMARAN, Darío Antonio. Malignant Tumor Derived from Skin Melanocytes of a Bovine of Unusual Presentation: A Case Study. Rev. Med. Vet. [online]. 2015, n.29, pp.63-72. ISSN 0122-9354.

Melanocytic tumors and melanomas in domestic animals include neoplasms composed of melanin-producing cells. In cattle, these tumors are rare and mostly benign, while malignant tumors are almost non-existent. The article reports the case of a female crossbred cow 38 months of age with a fluctuating mass located between the mandibular border and the left parotid region, about three months duration, with evident growth in the last thirty days. After surgical excision, a sample preserved in buffered formalin (10%) was sent to the Laboratory of Pathology (University of Nariño)-consisting of a fragment of 7.0 x 10.5 x 8.0 cm, ellipsoid, with skin and hair on one side, irregular surface, blackish brown, semi-soft consistency, and presence of shear translucent slimy content-for processing and inclusion in paraffin, cut to 5 µm thickness and stained with hematoxylin-eosin coloration. The forwarded tissue was classified as a neoplasm of malignant behavior derived from melanocytes, due to its cellular characteristics: growth pattern, pattern of distribution, severe cellular pleomorphism, anisocytosis, megalocytosis, nuclear pleomorphism, anisokaryosis, megalokaryosis, and involvement of blood vessel walls; additionally, the paraffin block was cut for immunohistochemical processing using monoclonal markers (S-100 DAKO® and Melan A DAKO®), contrasted with Mayer's hematoxylin. Strong immunostaining of neoplastic cells is evident, and it constitutes the first reported case of this disease in Nariño (Colombia).

Palavras-chave : immunohistochemistry; tegument; melanoma; neoplasia; cow.

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