Clinical Understanding and Diagnosis of Canine Transmissible Venereal Tumour (CTVT)

Canine Transmissible Venereal Tumour (CTVT), also known as Sticker’s sarcoma or infectious sarcoma, represents a rare yet clinically significant neoplastic condition in veterinary oncology. Unlike conventional tumours, CTVT is a contagious cancer transmitted through viable tumour cells, making it a major concern in free-roaming and sexually active dog populations. It most commonly affects the external genitalia, although extragenital involvement has also been reported in regions such as the oral cavity, nasal mucosa, and periocular tissues^1,2. 

From a clinical standpoint, the disease often presents dramatically, prompting immediate veterinary consultation due to its alarming appearance and associated bleeding. 

Etiopathogenesis: Beyond Conventional Oncology 

CTVT is a tumour of histiocytic origin, affecting dogs irrespective of breed, age, or sex, though it predominantly occurs in sexually active adults³. What sets this tumour apart is its mechanism of transmission. Rather than being caused by viral oncogenesis, current evidence strongly supports direct cell transplantation, where tumour cells themselves act as infectious agents^1,4. 

These cells possess the ability to evade host immune responses by bypassing the major histocompatibility complex (MHC) barrier. Additionally, they demonstrate chromosomal abnormalities, typically ranging between 57–64 chromosomes¹. 

A clinically important feature is the tumour’s immunosuppressive behavior. By inhibiting dendritic cell differentiation and suppressing T-cell infiltration, tumour cells create an environment conducive to unchecked proliferation⁵. This explains both disease persistence and occasional progression to malignancy. 

Clinical Presentation: Recognizing the Hallmarks 

Clinically, CTVT presents as friable, cauliflower-like masses that are often hemorrhagic and ulcerated. In males, lesions are typically located on the caudal penis, while in females, the posterior vaginal wall is commonly affected¹. 

Common signs include: 

• Bloody or serosanguinous discharge  

• Ulceration and swelling  

• Dysuria or difficulty in urination  

• Mating refusal and discomfort  

In advanced cases, systemic signs such as anorexia, weight loss, and weakness may also be observed. Importantly, urine retention can predispose affected animals to secondary infections like bacteriuria, complicating the clinical picture. 

Diagnostic Approach: Practical and Cost-Effective Tools 

For practicing veterinarians, early and accurate diagnosis is crucial. A stepwise diagnostic approach ensures both efficiency and accuracy. 

1. Exfoliative Cytology 

This is the most practical and cost-effective first-line diagnostic tool. Using Giemsa staining, characteristic round cells with vacuolated cytoplasm can be easily identified⁶. It is minimally invasive and ideal for field conditions. 

2. Histopathology 

Biopsy remains the gold standard for definitive diagnosis. Histological examination reveals densely packed tumour cells with large nuclei and scant cytoplasm, often arranged around vascular channels¹. 

3. Immunohistochemistry 

In suspected metastatic cases, immunohistochemistry aids in tumour confirmation and differentiation⁷. 

Differential Diagnosis: Avoiding Clinical Pitfalls 

CTVT must be differentiated from other round cell tumours, including: 

• Lymphoma  

• Histiocytoma  

• Mast cell tumours  

• Amelanotic melanoma  

• Carcinomas  

Misdiagnosis can significantly alter treatment outcomes, especially when differentiating from aggressive tumours like hemangiosarcoma¹. 

Clinical Relevance and Takeaway 

Understanding the unique biology of CTVT is critical for effective clinical management. Its contagious nature, immunosuppressive characteristics, and varied presentation demand a high index of suspicion. For clinicians, adopting simple diagnostic tools like cytology can significantly improve early detection rates. 

Ultimately, integrating pathophysiology with clinical findings allows veterinarians to not only diagnose accurately but also contribute to better disease control at a population level.  

References: 

1. Biswas N, Singh K, Kumar S, Parmar S, Srivastava N, Khan MH. Therapeutics and Management of Persistent Cases of Canine Transmissible Venereal Tumour: An Update. Animal Reproduction Update. 2024 Jul 1;4(2). https://www.researchgate.net/profile/Newton-Biswas/publication/381583366_Therapeutics_and_Management_of_Persistent_Cases_of_Canine_Transmissible_Venereal_Tumour_An_Update/links/667537771846ca33b842ba3a/Therapeutics-and-Management-of-Persistent-Cases-of-Canine-Transmissible-Venereal-Tumour-An-Update.pdf 

2. Setthawongsin C, Techangamsuwan S, Rungsipipat A. Canine transmissible venereal tumor: An infectious neoplasia in dogs. In Recent in Advances Canine Medicine. IntechOpen 2022.  https://doi.org/10.5772/intechopen.106150.  

3. Alkan H, Satilmis F, Alcigir ME, Kivrak MB, Aydin I. Clinicopathological evaluation of disseminated metastases of transmissible venereal tumor in a spayed bitch. Acta Sci Vet. 2017; 45(S1): 1-6. https://www.redalyc.org/pdf/2890/289050563012.pdf 

4. Çizmeci SÜ, Guler M. Transmissible venereal tumour (TVT) in bitches and therapy: a review. Malays J Vet Res. 2018; 9: 136–43. https://research.dvs.gov.my/portal/wp-content/uploads/2021/12/MJVR-V9N2-p136-143.pdf 

5. Abeka YT. Review on canine transmissible venereal tumor (CTVT). Ther Oncol Int J.  2019; 14(4): 1-9. https://www.researchgate.net/profile/Yimesgen-Abeka/publication/336741853_Review_on_Canine_Transmissible_Venereal_Tumor_CTVT/links/5db050044585155e27f80d10/Review-on-Canine-Transmissible-Venereal-Tumor-CTVT.pdf?_sg%5B0%5D=started_experiment_milestone&origin=journalDetail 

6. Priyadarshini N, Das DP, Panda SK, Samal L. Transmissible venereal tumours (TVT) in bitches: A haematological, biochemical and histopathological study. J Entomol Zool Stud. 2021; 9(1): 490-493. https://www.academia.edu/download/95509819/9-1-102-617.pdf 
7. Küçükbekir ÇN, Uçmak ZG, Tek Ç. Canine transmissible veneral tumor: etiology, diagnosis and treatment. J Istanbul Vet Sci. 2021; 5(1): 57-65. https://dergipark.org.tr/en/download/article-file/1584817