Contagious Tumors: Do they exist in dogs?

Known as a canine transmissible venereal tumor, this disease can be transmitted through contact with an infected dog by sniffing, licking, or during intercourse.
Contagious Tumors: Do they exist in dogs?

Last update: 19 October, 2018

In the dog world, there are some types of contagious tumors, which are actually a unique form of cancer. A transmissible venereal tumor (TVT) is a cancerous growth that only develops in dogs and, unlike other types of tumors, they’re contagious.

What are contagious tumors?

Venereal tumors are the oldest known form of cancer and only dogs contract them. However, there are other animal species, such as Syrian hamsters and clams, can also develop contagious forms of cancer.

Known as a canine transmissible venereal tumor, this disease can be transmitted through contact with an infected dog by sniffing, licking, or during intercourse.

The infection can be very powerful inside an animal’s body. In such cases, the disease has managed to evolve to survive outside of the body it has originally infected.

Dog lying down on grass.

How do dogs get malign tumors?

Venereal tumors are normally contracted during the act of intercourseor when one dog smells or licks any infected mucous.  This is why this type of tumor tends to develop around a dog’s genital area, although it can affect other places as well, such as the nose.

What’s interesting about these contagious tumors is that their behavior is completely different and unique when compared with the majority of types of tumors that affect other animals. These types of tumor have evolved to spread to new tissues which allow them to continue developing.

Dogs contract this illness when they come into contact with cancerous cells from another dog. It doesn’t need a virus or any other kind of contagion. Upon contact on the skin, cancerous cells will spread from animal to animal and they can live for a much longer time.

Patient Zero

Several different studies have concluded that these types of tumors have a DNA that’s different to the carrier. The majority of tumors form when cells uncontrollably mutate. Because of this, tumors normally have the same DNA as the patient. However, with venereal tumors, this doesn’t happen.

Researchers estimate that this type of tumor developed around 11,000 years ago. It has continued to evolve and adapt which is why it’s so persistent.

This form of tumor actually responds very well to treatment0, so it’s unlikely to metastasize. However, there is always a possibility. If you compare it to other types of tumor, TVT is one of the least aggressive.

Jack Russell wrapped up in a blanket

Is it possible to prevent TVT?

Dog owners can take preventive measures to prevent their pets from being exposed to the contagion. One of the best treatments you can do is to neuter your dog  The ideal age to do this is between the age of 12 months or 8 months old for large dog breeds

Getting your pet neutered is very important because this disease can spread easily during intercourse. Neutering removes the reproductive organs and reduces the probability of your dog becoming infected.

At the same time, it’s a good idea to keep your dog in a controlled environment. You should also take your dog to the vet on a regular basis, especially if you notice any significant changes. It’s not always easy to locate the symptoms of an internal tumor.

However, when it comes to  TVT, dogs tend to develop a bleeding red patch. Practicing good hygiene is important for both you and your dog is a key factor in staying healthy.


Contagious tumors definitely do exist.  It’s a type of venereal cancer which is normally transmitted during intercourse.

However, to a lesser extent, transmission can also occur through smelling or licking the affected area. Therefore, you can neuter your dog and keep him in a controlled area to prevent him from developing this type of tumor.