Venereal squamous papilloma in a male dog

A dog (Maltese, 4-year-old, intact male) was referred to the hospital because of the multiple cabbage-shaped nodular masses on penis, preputial fornix and inner layer of prepuce with the free-roaming history. Those appearance was similar with the characteristic of transmissible venereal tumor (TVT). As a result, it was tentatively diagnosed as TVT by the veterinarian of a local clinic and treated with vincristine sulfate. However, the lesion did not regress. Histologically, the mass was consisted of fibrovascular connective tissue stalks and keratinized stratified squamous epithelium, and koilocytosis and intranuclear inclusion body were not shown in the epithelial layer. In addition, inflammatory changes were minimal in the tissue of mass. Based on these findings, this case was diagnosed as venereal squamous papilloma. As the treatments of TVT and papilloma differs, practitioners must be cautious with the diagnosis.