Clinico-Pathology and Therapeutic Management of a Primary Atypical Extra-Genital Ocular Transmissible Venereal Tumour in a Dog in Lusaka, Zambia

Abstract

<jats:p>Canine Transmissible Venereal Tumour (CTVT) is a contagious cancer commonly found in the genitalia of dogs, with rare extra-genital presentations, such as cutaneous, oral, nasal, and ocular forms. Extra-genital CTVT cases, especially in the ocular region, are infrequently reported, often leading to diagnostic challenges and underdiagnosis in regions with high prevalence.A two-year-old male German Shepherd mix was presented to the University of Zambia, School of Veterinary Medicine, with a red, lobulated mass originating from the third eyelid of the right eye, causing partial vision loss and continuous lacrimation. Initial clinical examination suggested ocular squamous cell carcinoma. However, cytology and histopathology findings from a tissue biopsy revealed round and ovoid neoplastic cells with large pleomorphic nuclei, leading to a definitive diagnosis of primary ocular CTVT. The dog exhibited no genital involvement or evidence of tumour spread to other sites. The dog was treated with vincristine sulphate administered intravenously in six doses over six weeks. Following the second dose, the patient experienced leukopenia, thrombocytopenia, decreased appetite, and weight loss, all common side effects of vincristine. Supportive care, including antibiotics, fluid therapy, and appetite stimulants, was provided, resulting in improved condition. By the end of the treatment, the ocular mass had completely regressed, vision was restored, and the dog remained in remission with no recurrence observed after twelve months. This case represents the first reported instance of primary ocular CTVT in Zambia without genital involvement. The successful use of vincristine sulphate highlights its efficacy in treating extra-genital CTVT forms. Given CTVT’s potential for atypical presentations, it is crucial for veterinarians in endemic areas to consider it in the differential diagnosis of extra-genital ocular masses to prevent under diagnosis and ensure timely treatment.</jats:p>