RESUMEN
Canine transmissible venereal tumor (CTVT) is a contagious tumor commonly seen in populations of sexually intact dogs that have close contact with each other. CTVT is one of only 3 known naturally transmissible, contagious tumors in which the mutated tumor cell is thought to have originated in an individual canid about 11000 years ago. Clinical history, signalment, cytological and histologic evaluation are typically sufficient for reaching a diagnosis, although immunohistochemistry(IHC) may be necessary for unique presentations of this neoplasm. This case report describes the diagnosis of an oronasal CTVT using histopathology and IHC, followed by treatment of the tumor with chemotherapy and surgical correction of a defect caused by the tumor.