Canine Transmissible Venereal Tumors: These Tumors Can Be Spread

The probability is that you have never seen a tumor that can be spread from one individual to another. But did you know that there is a tumor that can be transmitted from dog to dog? 

Transmissible Venereal Tumor (TVT) is a tumor of dogs that is surprisingly common and widely distributed. Canine TVT occurs primarily in dogs that are largely uncontrolled and allowed to breed indiscriminately. It also affects other canids such as coyotes, foxes and jackals.

Also known as infectious sarcoma, venereal granuloma, transmissible lymphosarcoma or Sticker tumor, this disease is a benign tumor that occurs primarily on the external genitals of both male and female dogs. It is one of a very few tumors that can be transmitted by direct contact. It acts like a freely living organism -- more a parasite than a cancer.

What does TVT look like? 
Canine TVT is cauliflower-like, pedunculated, nodular, papillary, or multilobulated in appearance. It ranges in size from a small nodule (5 mm) to a large mass1. Finding a small nodule that bleeds and is located on the external genitalia is the most consistent symptom. The condition is transmitted during sexual contact and is most commonly seen in young, but mature, sexually active animals.

How does a dog become affected? 
Transmission occurs during direct contact with other dogs2. Elizabeth Murchison, a cancer biologist at the Wellcome Trust Sanger Institute in Hinxton, UK says, “It’s the oldest continuously surviving cancer we know of in nature.” It first appeared in an ancient breed of dog, not unlike the Alaskan malamute, that was of medium to large size. TVT remained in an isolated population of dogs for most of its history, then something happened that allowed it to move into other dog populations and spread around the world3. “These tumors are masters at survival, at transmission and at invading new tissues,” says Hannah Siddle, a tumor immunologist at the University of Southampton, UK, who studies contagious cancers.

How is the TVT diagnosed? 
Your veterinarian must perform a biopsy or examination of cells from the mass to be sure it's TVT.

What is the prognosis with TVT?
Initially, TVTs grow rather fast and more rapidly in neonatal and immuno-suppressed dogs. Metastasis (spreading) is uncommon (5%). Many cases resolve spontaneously and self cure. Complete surgical removal is difficult and recurrence is likely. Radiation therapy is effective but the tumor is very responsive to chemotherapy1.  Currently a drug called Vincristine is helpful with a period of 6-7 weeks as the recommended treatment.

Is TVT transmissible to humans?
There is no risk of transfer of the tumor to humans. 

Can the condition be prevented?
Since the method of transmission is direct sexual contact, prevention of coatis is the best means of prevention.

See your veterinarian right away for any lesions. An early diagnosis and prompt treatment reduces the course of most diseases.

If you have any questions or concerns, you should always visit or call your veterinarian -- they are your best resource to ensure the health and well-being of your pets.

1. "Overview of Canine Transmissible Venereal Tumor." Merck Veterinary Manual. Web.

2. "Canine Transmissible Venereal Tumor: A Review." Internet Scientific Publications. Web. 

3. Borrell, Brendan. "How a Contagious Dog Tumor Went Global." Nature Publishing Group, 23 Jan. 2014. Web.


Reviewed on: 
Sunday, December 7, 2014