DESAFIO DIAGNÓSTICO EM ONCOLOGIA VETERINÁRIA: relato de neoplasia mesenquimal maligna em cadela inicialmente suspeita de TVT

Abstract

The diagnosis of neoplasms in veterinary oncology represents a constant challenge, especially in anatomical regions where different tumor types may coexist. Vaginal neoplasms in female dogs, although uncommon, include Transmissible Venereal Tumor (TVT) as an important differential diagnosis due to its high prevalence. This study aimed to report a case of malignant mesenchymal neoplasm in a female dog, whose initial clinical and cytological presentation suggested TVT, highlighting the limitations of cytology alone and the importance of combining histological, histochemical, and immunohistochemical methods for diagnostic confirmation. This is a descriptive and observational case report based on a retrospective analysis of clinical, laboratory, and histopathological data from a nine-year-old Poodle presenting persistent vaginal bleeding. Lack of response to chemotherapy prompted diagnostic reassessment using histopathological, histochemical, and immunohistochemical analyses. Histopathology revealed a proliferation of spindle-shaped cells arranged in bundles, moderately stained red by Masson’s trichrome, supported by a delicate collagen stroma, with positive immunolabeling for vimentin and negative for cytokeratin, CD31, VEGF, and Melan-A, consistent with a malignant mesenchymal neoplasm of smooth muscle origin, suggestive of vaginal leiomyosarcoma. It is concluded that accurate diagnosis of neoplasms in small animals depends on the integration of clinical evaluation, imaging, and complementary laboratory analyses, reinforcing the importance of a multidisciplinary approach for effective oncologic management.