Aspectos epidemiológicos, fatores de risco e achados clinicopatológicos do melanoma em cães no Sertão, Nordeste do Brasil

Abstract

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: Biopsies and necropsies performed on dogs at the Animal Pathology Laboratory of the Federal University of Campina Grande during the period from 2000 to 2021 were reviewed. 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 one (2.1%) was young. Mixed breed animals were the most affected (42.6%), followed by the pinscher breed (19.1%). The neoplasms were in the skin, oral cavity, and eyeball. In nine (18.75%) cases, metastases were identified, eight in lymph nodes and one in the lung. The lesions were located mainly on the skin and were characterized by a nodular and blackened growth pattern. 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 Sertão 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.