Transmissible Venereal Tumor (TVT) in Dogs

What Is a Transmissible Venereal Tumor (TVT) in Dogs?

TVT is a transmissible cancer in dogs that’s usually spread via direct contact with the tumor during mating. The likelihood of this tumor varies dramatically based on geographic location. For example, while rare in most of the continental United States, in other countries such as India there can be a high prevalence of TVT among stray dogs.

Dogs with this tumor develop painful masses that protrude from the vulva or penis. Sometimes this tumor can be found on the nose, mouth, eyes, or skin if the dog sniffs or licks the tumor of another dog.

While it’s normal to be alarmed when you notice a new growth on your dog, TVT typically warrants making a veterinary appointment rather than visiting an emergency clinic. However, if your dog is in pain or can’t stop licking at the tumor, you may consider urgent care to get relief immediately.  

TVT can be found worldwide but is most common in tropical and subtropical urban environments. It is one of just three known transmissible cancers. The other two are Tasmanian devil facial tumor disease and leukemia in many marine bivalves, including clams, mussels, and oysters.

Symptoms of TVT in Dogs

Tumors on the genitals may have the following signs:

• Gray or pinkish-gray color

• Bleed easily when touched

• Cauliflower-like “stalk” appearance

• Firm but easily friable texture (it may bleed or tear easily)

• Bleeding from the genitals

• Licking at genitals

• Swelling of genitals

When tumors are on the mouth or nose, in addition to the nodular masses, you may also notice:

• Bleeding from the nose (epistaxis)

• Sneezing

• Bad breath

• Excessive drooling

• Loss of teeth

• Sores on the gums or palate

On the skin, these nodules often develop open sores, and nearby lymph nodes might become enlarged.

Causes of TVT in Dogs

Transmissible venereal tumor in dogs is usually spread during mating. While it’s common to see the masses on the external genitals, it can also affect the internal genitals. The cancer passes between animals more easily if there are abrasions in the mucosal surface of the genitals.

TVT can also develop in other parts of the body through social behaviors like licking or sniffing another dog’s tumor.

Currently, it’s not known what cell type TVT originates from. Interestingly, TVT cancer cells have fewer chromosomes (around 59) compared to a dog’s normal cells, which have 78 chromosomes. It’s suspected that the disease first developed thousands of years ago in wolves or wild dogs.

No breeds are predisposed. Young, sexually active (not neutered or spayed), stray dogs are more likely to be affected. TVT affects both sexes, though females reportedly have a higher likelihood.

How Veterinarians Diagnose TVT in Dogs

The tumor is usually suspected based on the animal’s history, location on the body, and appearance of the mass.

Your vet will want a diagnostic sample by pressing a slide to the tumor or placing a needle into the tumor to aspirate some cells, then examining the cells under a microscope.

A diagnosis is made by sending a small sample of the tumor to a reference laboratory for examination under a microscope. Taking a biopsy sample requires sedation and is usually a minor surgical procedure. At the reference laboratory, a staining procedure called immunohistochemistry may be performed on tumor samples to determine how aggressive the tumor is.

With TVT, metastasis (spread to other parts of the body) doesn’t usually occur. In cases where it’s suspected, the veterinarian may take samples of the lymph nodes, recommend X-rays of the chest, and recommend an ultrasound of the abdomen.

Treatment of TVT in Dogs

Surgical removal of the mass is an option if the mass is small (less than 2 centimeters in diameter) and in an accessible location. Surgery isn’t usually an option for tumors that are large, affecting the internal genitals, and/or affecting other areas like the inside of the nose.

For single tumors, injecting the chemotherapy medication vincristine into the tumor for one to four treatments, as well as interleukin-2 (a compound that mediates interactions between white blood cells), is usually quite effective. One treatment cycle is often sufficient.

If the dog has evidence of metastatic TVT (where the tumor has spread to other parts of the body) or has multiple tumors, the treatment of choice is intravenous vincristine chemotherapy given once weekly for up to six weeks. Your dog will need to be monitored to ensure they are tolerating chemotherapy, which can affect their immune system by decreasing white blood cell counts.

While radiation therapy can be highly effective, it’s restricted to specialized facilities. In some cases, one radiation session can treat the tumor.

In the rare cases where spontaneous regression (a decrease in size of the tumor) does occur, it usually begins within three months of transmission. If the dog has had the tumor for nine months with no evidence of regression, it is unlikely to happen at all.  Most TVTs require intervention, so pet parents of dogs with TVT should follow their veterinarian’s recommendations as soon as possible.

Recovery and Management of TVT in Dogs

With recommended treatment, the prognosis for TVT is good in otherwise healthy dogs, regardless of where the tumor is located or whether it has metastasized. Rarely, highly aggressive tumors can be fatal, especially when untreated.

Pet parents should be aware that their dog can get TVT again after the initial TVT was cured. To reduce the likelihood of spreading this tumor, pet parents must prevent contact between their pets and stray dogs. Spaying and neutering also decreases the risk of cancer spreading between dogs.

If your dog has TVT, do not allow them to have contact with other dogs until the veterinarian confirms that the disease has been cured.

Without surgery or medical intervention, most dogs will continue to have the tumor. These tumors may become resistant to treatment and your dog could spread the tumor to other dogs. 

 These tumors are uncomfortable for your canine companion. The masses often develop sores and bleed, and your pet may want to lick them. Some pets may need anti-inflammatory medications like carprofen to help decrease pain and inflammation.

Others may need an Elizabethan collar (e-collar or cone) to keep them away from the area. The tumor may also predispose your dog to a urinary tract infection. Speak with your veterinarian if your pet seems bothered by their TVT.