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