Transmissible Venereal Tumors in Dogs: A 2025 Vet Oncology Guide by Dr Duncan Houston 🧬🐕

By Dr Duncan Houston, BVSc | July 2025

🦠 What Is a Transmissible Venereal Tumor (TVT)?

Transmissible venereal tumors (TVTs) are contagious tumors that spread between dogs through physical contact, typically during mating or genital sniffing. The tumor grows on mucous membranes like the genitals, mouth, nose, or anus and can be transmitted when a tumor from one dog contacts an abrasion or moist tissue on another. 📉

📸 Where TVTs Are Found

TVTs are most common in areas with large populations of roaming or shelter dogs. The tumors appear as:

🔴 Fleshy, red, or ulcerated growths
🩸 Persistent genital bleeding
👃 Nasal discharge or swelling if tumors are on the face

🧬 How TVT Spreads

Unlike most cancers, TVT is not a virus—it is literally transplanted tumor tissue from one dog to another. These tumor cells have a different number of chromosomes from their host and act like a graft, not a mutation. Think of it as a living tumor passed between dogs. 🧫

🧪 Diagnosing TVT

Your veterinarian may perform:

🔬 Cytology: Smearing tumor cells and viewing under a microscope
🔍 Biopsy: Taking a tissue sample to confirm tumor type

TVTs are a type of round cell tumor and are usually easy to identify with basic cytology. 📑

💊 Treatment Options

1. 💉 Vincristine Chemotherapy (Gold Standard)

🔹 Weekly IV injections (typically 3–6 treatments)
⚠️ Must be administered carefully to avoid tissue damage from leakage
🌟 Tumors often shrink dramatically after 1–2 doses
🧪 Can be combined with NSAIDs for faster response

2. 💉 Doxorubicin

💪 Stronger chemo for vincristine-resistant cases
🏥 Also given IV under careful monitoring

3. 🔦 Radiation Therapy

📍 Highly effective but less available
💸 Expensive and requires referral to a specialty center

4. 🔪 Surgery (Not Recommended Alone)

Surgical removal often leads to tumor recurrence in 20–25% of dogs. If surgery is done, follow-up with chemo is advised. 🏥

📈 Prognosis

With chemotherapy, especially vincristine, the prognosis is excellent. Most dogs are cured after a few treatments and live normal lives. 🐾

📋 TVT Summary Table

Aspect	Details
Transmission	Direct contact (mating, sniffing)
Common Sites	Genitals, mouth, nose, anus
Diagnosis	Cytology or biopsy
Best Treatment	Vincristine chemotherapy
Prognosis	Excellent with treatment

🛡️ Prevention Tips

🚷 Avoid contact between dogs in areas where TVT is common
🔄 Spay/neuter dogs to reduce roaming and mating behavior
🏥 Regular health checks for shelter or street dogs

🔧 Ask A Vet Can Help

Not sure if your dog has a transmissible tumor? Use the Ask A Vet app to upload photos, share symptoms, and get fast answers about diagnosis and treatment plans. 🐶📱

🐾 Final Thoughts from Dr Duncan Houston

TVT is one of the few contagious cancers in the animal kingdom—but it’s also one of the most treatable. With early detection and proper care, most dogs recover fully and live happy, healthy lives. 💙

— Dr Duncan Houston, BVSc

Visit AskAVet.com or download the Ask A Vet app for support with cancer diagnosis, chemotherapy planning, and follow-up care. 📱