Melanoma in Dogs in the Backlands of Northeastern Brazil - Epidemiology, Risk Factors and Clinicopathological Findings




Background: Melanoma is a malignant neoplasm that arises from melanocytes and malanoblasts. It is also more frequently reported in dogs than in other species. They may arise from melanocytes in the skin, on the surfaces of the mucous membranes, and eyes. The aim of this study was to describe the epidemiological aspects, risk factors and clinicopathological findings of melanoma in dogs in the backlands, northeastern Brazil.

Materials, Methods & Results: A retrospective study was carried out in all biopsy samples and necropsy examinations of dogs, from January 2003 to December 2021, at the Animal Pathology Laboratory of the Federal University of Campina Grande, Patos, Paraiba, northeastern Brazil. Epidemiological data, clinical signs, and gross lesions were reviewed from the diagnostic laboratory reports. Samples of the skin, lymph nodes, central nervous system and organs of the thoracic and abdominal cavities were fixed in 10% buffered formalin, processed routinely for histopathology, embedded in paraffin wax, cut into 4 µm sections, and stained with hematoxylin and eosin (HE). Histological sections were also submitted to immunohistochemistry with the primary antibody anti-Melan A. Of the 4717 records found, 1158 (24.5%) were diagnosed with neoplasms, of which 48 (4.14%) cases were of melanoma. Of this total, 28 (58.3%) dogs were elderly, 19 (39.6%) were adults, and 1 (2.1%) was young. Mixed breed animals were the most affected (42.6%), followed by the pinscher breed (19.1%). According to the anatomical region, the most affected site was the skin (38/53=71.7%), followed by the oral cavity (12/53=22.65%) and the eyes (3/53=5.7%). Grossly, the skin lesions were characterized by exophytic and usually blackened, sometimes irregular and firm, nodules. At cut, they had a smooth, compact and blackened surface. Lesions in the oral cavity were characterized by blackened, irregular and infiltrating nodules or masses. The ocular lesions were always unilateral and were characterized by an enlarged and diffusely blackened eyeball, with areas of ulceration and subversion of tissue architecture. In 5 animals there was more than one anatomical site affected, totaling 53 lesions. In 9 (17%) cases, metastases were identified, 8 in regional lymph nodes and 1 in the lung. Histopathology showed a densely non-encapsulated, poorly delimited, expansive and infiltrative neoplasm, composed of neoplastic cells arranged in islands or nests and supported by fibrovascular stroma, containing a variable amount of brownish pigment (melanin). Immunohistochemistry showed strong immunostaining of the neoplastic cells in brown by the anti-Melan A antibody.

Discussion: The diagnosis of melanoma was established based on epidemiological, clinical, anatomopathological, and immunohistochemical findings. Gender is not a predisposing factor, and although there was no statistically significant relationship, males were more affected. Senescence is a conditioning risk factor. Elderly animals were more affected (P < 0.0001) than adult ones, with OR = 4.38; and young ones (P = 0.0051), with OR = 12.65. Some breeds, especially those with marked skin pigmentation, were more affected, however the most affected ones in this survey were pinscher and poodle. Cutaneous melanoma accounted for almost 72% of cases, contesting recent studies where oral cavity melanoma was more frequent. Therefore, it is believed that the climatic conditions of the backlands sub-region, in northeastern Brazil, associated with the individual characteristics of the dogs, are involved in the development of these neoplasms, since the climate is predominantly dry, with high temperatures throughout the year, with maximums that can reach 40ºC, favoring the exposure to high incidence of ultraviolet radiation.

Keywords: dog disease, dermatopathy, neoplasm, melanocytes.

Título: Melanomas em cães no Sertão do Nordeste do Brasil - epidemiologia, fatores de risco e achados clinicopatológicos

Descritores: doença de cão, dermatopatia, neoplasma, melanócitos.


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Armstrong B.K. & Kricker A. 2001. The epidemiology of UV induced skin cancer. Journal of Photochemistry and Photobiology B: Biology. 63(1): 8-18.

Baptista A.C., Marchiori E., Boasquevisque E. & Cabral C.E.L. 2003. Proptose ocular como manifestação clínica de tumores malignos extra-orbitrários: Estudo pela tomografia computadorizada. Radiologia Brasileira. 36: 81-88.

Bastian B.C. 2014. The molecular pathology of melanoma: an integrated taxonomy of melanocytic neoplasia. Annual Review of Pathology. 9(1): 239-271.

Bedoya S.A. 2019. Estudo retrospectivo de neoplasias melanocíticas cutâneas espontâneas em cães: caracterização histopatológica, morfométrica e sequenciamento de TP53. 82f. Tese (Doutorado em Medicina Veterinária) - Programa de Pós-Graduação em Ciências Veterinárias, Universidade Federal de Viçosa.

Bistner S.I. 2007. Olho e órbita. In: Slatter D.H. (Ed). Manual de Cirurgia de Pequenos Animais. 3.ed. Barueri: Manole, pp.2430-2432.

Camargo L.P., Conceição L.G. & Costa P.R.S. 2008. Neoplasias melanocíticas cutâneas em cães: estudo retrospectivo de 68 casos (1996-2004). Brazilian Journal of Veterinary Research and Animal Science. 45: 138-152.

Chénier S. & Doré M. 1999. Oral Malignant Melanoma with Osteoid Formation in a Dog. Veterinary Pathology. 36: 74-76.

Dobson J.M. 2013. Breed-predispositions to cancer in pedigree dogs. ISRN Veterinary Science. 2013: 941275.

Dubielzig R.R. 2002. Tumors of the eye. In: Meuten D.J. (Ed). Tumors of Domestic Animals. 4th edn. Ames: Iowa State Press, pp.739-754.

Farias Neto J.R. 2020. Caracterização e tendências climáticas da cidade de Patos (Paraíba) e consequências para a energia fotovoltaica. 94f. Dissertação (Mestrado em Engenharia Mecânica) - Programa de Pós-Graduação em Engenharia Mecânica, Universidade Federal da Paraíba.

Freitas S.H., Dória R.G.S., Pire M.A.M., Mendonça F.S., Camargo L.M. & Evêncio Neto J. 2007. Melanoma oral maligno em cadela relato de caso. Veterinária em Foco. 5: 16-21.

Goldschmidt M.H. & Goldschmidt K.H. 2017. Epithelial and Melanocytic Tumors of the Skin. In: Meuten D.J. (Ed). Tumors in Domestic Animals. 5th edn. Ames: John Wiley & Sons, pp.88-141.

Goldschmidt M.H. & Hendrick M.J. 2002. Tumors of the skin and soft tissues. In: Meuten D.J. (Ed). Tumors in Domestic Animals. 4th edn. Ames: Iowa State Press, pp. 44-117.

Kok M.K., Chambers J.K., Tsuboi M., Nishimura R., Tsujimoto H., Uchida K. & Nakayama H. 2019. Retrospective study of canine cutaneous tumors in Japan, 2008-2017. Journal of Veterinary Science. 81(8): 1133-1143.

Leite-Filho R.V., Panziera W. & Bandinelli M.B. 2020. Epidemiological, pathological and immunohistochemical aspects of 125 cases of feline lymphoma in Southern Brazil. Veterinary and Comparative Oncology. 2: 224-230.

Lima S.R. 2018. Cutaneous neoplasms in dogs: 656 cases (2007-2014) from Cuiabá, MT. Pesquisa Veterinária Brasileira. 38(7): 1405-1411.

Lindoso J.V.S., Rufino A.K.B., Silva Luz P.M., Silva T.S., Sousa Júnior F.L., Sousa F.B. & Sales K.K.S. 2017. Melanoma metastático em cão: Relato de caso. Pubvet. 11(4): 346-350

Linos E., Swetter S.M., Cockburn M.G., Colditz G.A. & Clarke C.A. 2009. Increasing burden of melanoma in the United States. The Journal of Investigative Dermatology. 129(7): 1666-1674.

London C. 2004. Biologia do tumor. In: Ettinger S.J. & Feldman E.C. (Eds). Tratado de Medicina Interna Veterinária: Doenças do Cão e do Gato. 5.ed. Rio de Janeiro: Guanabara Koogan, pp.506-512

Manzan R.M. 2005. Considerações sobre Melanoma Maligno em cães: uma abordagem histológica. Boletim de Medicina Veterinária. 1(1): 41-47.

Martins T.B. & Barros C.S.L. 2014. Fifty years in the blink of an eye: a retrospective study of ocular and periocular lesions in domestic animals. Pesquisa Veterinária Brasileira. 34(12): 1215-1222.

Meirelles A.E.W.B., Oliveira E.C., Rodrigues B.A., Costa G.R., Sonne L., Tesser E.S. & Driemeier D. 2010. Prevalência de neoplasmas cutâneos em cães da Região Metropolitana de Porto Alegre, RS: 1.017 casos (2002-2007). Pesquisa Veterinária Brasileira. 30(11): 968-973.

Modiano J.F., Ritt M.G. & Wojcieszyn J. 1999. The molecular basis of canine melanoma: pathogenesis and trends in diagnosis and therapy. Journal of Veterinary Internal Medicine. 13(3): 163-174.

Nakhleh R.E. 1990. Morphologic diversity in malignant melanomas. American Journal of Clinical Pathology. 93: 731740.

Nishiya A.T., Massoco C.O., Felizzola C.R., Perlmann E., Batschinski K., Tedardi M.V., Garcia J.S., Mendonça P.P., Teixeira T.F. & Zaidan Dagli M.L. 2016. Comparative Aspects of Canine Melanoma. Veterinary Sciences. 3(1): 7-22.

Oliveria S.A., Saraiya M., Geller A.C., Heneghan M.K. & Jorgensen C. 2006. Sun exposure and risk of melanoma. Archives of Disease in Childhood. 91(2): 131-138.

Ramos-Vara J.A., Beissenherz M.E., Miller M.A., Johnson G.C., Pace L.W., Fard A. & Kottler S.J. 2000. Retrospective Study of 338 Canine Oral Melanomas with Clinical, Histologic, and Immunohistochemical Review of 129 Cases. Veterinary Pathology. 37(6): 597-608.

Rodrigues A.C., Castro M.R., Viscone E.A., Oliveira L.A. & Medeiros A.A. 2017. Melanoma em cão com múltiplas metástases: Relato De Caso. Enciclopédia Biosfera. 14: 904-910.

Rolim V.M., Casagrande R.A., Watanabe T.T., Wouters A.T., Wouters F., Sonne L. & Driemeier D. 2012. Melanoma amelanótico em cães: estudo retrospectivo de 35 casos (2004-2010) e caracterização imuno-histoquímica. Pesquisa Veterinária Brasileira. 32(4): 340-346

Santos I.R., Lima A.C.M.P., Ferreira H.H., Rezende B.R., Silva A.R. & Santos A. S. 2020. Canine cutaneous neoplasms in the metropolitan region of Goiânia, Goiás State, Brazil. Pesquisa Veterinaria Brasileira. 40(8): 614-620.

Schultheiss P.C. 2006. Histologic features and clinical outcomes of melanomas of lip, haired skin, and nail bed locations of dogs. Journal of Veterinary Diagnostic Investigation. 18: 422-425.

Scott D.W., Miller W.H. & Griffin C.E. 2001. Neoplastic and Non-Neoplastic Tumors. In: Miller W.H., Griffin C.E. & Campbell K.L. (Eds). Muller and Kirk’s Small Animal Dermatology. 6th edn. Philadelphia: W.B. Saunders, pp.813-841.

Silva A.P.T. Sawada M.L., Pinheiro A.O., Torres M.L.M. & Balieiro P.C.O. 2013. Melanoma ocular em cães: relato de dois casos. Revista de Educação Continuada em Medicina Veterinária e Zootecnia do CRMV-SP. 11(1): 24-31.

Simpson R.M., Bastian B.C., Michael H.T., Webster J.D., Prasad M.L., Conway C.M., Prieto V.M., Gary J.M., Goldschmidt M.H., Esplin D.G., Smedley R.C., Piris A., Meuten D.J., Kiupel M., Lee C.C., Ward J.M., Dwyer J.E., Davis B.J., Anve M.R., Molinolo A.A. & Hewitt S.M. 2014. Sporadic naturally occurring melanoma in dogs as a preclinical model for human melanoma. Pigment Cell & Melanoma Research. 27(1): 37-47.

Smith S.H., Goldschmidt M.H. & Mcmanus P.M. 2002. A comparative review of melanocitic neoplasms. Veterinary Pathology. 39: 651-678.

Teixeira T.F., Silva T.C.D., Cogliati B., Nagamine M.K. & Dagli M.L.Z. 2010. Retrospective study of melanocytic neoplasms in dogs and cats. Brazilian Journal of Veterinary Pathology. 3(2): 100-104.

van der Weyden L., Brenn T., Patton E.E., Wood G.A. & Adams D.J. 2020. Melanoma de ocorrência espontânea em animais e sua relevância para o melanoma humano. The Journal of Pathology. 252(1): 4-21.

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Lopes de Lima, A., Platini Ferreira de Souto, E. ., Norberto de Oliveira, L., dos Santos Carneiro, R. ., Noronha de Toledo, G. ., José Nogueira de Galiza, G. ., & Medeiros Dantas, A. F. . (2022). Melanoma in Dogs in the Backlands of Northeastern Brazil - Epidemiology, Risk Factors and Clinicopathological Findings. Acta Scientiae Veterinariae, 50.




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