While this type of tumor has been diagnosed throughout many areas of the world, it seems to favor temperate climates, such as the United States, Southern Europe, Asia, Africa, and the Caribbean. It is believed that transmissible venereal tumors (TVT) are the oldest known form of cancer, and first emerged 11,000 years ago. All TVT tumors contain DNA belonging to the first dog infected with this cancer, and researchers are analyzing the mutations seen in these tumors to figure out how TVT first developed and spread.

Transmissible venereal tumors are a cancer that causes nodular tumors in sexually active dogs of both sexes, often in the genital area. This sexually transmitted disease is also referred to as Sticker’s sarcoma, venereal granuloma, infective venereal tumor, and transplantable lymphosarcoma. Tumors of this type are common in stray, roaming dogs, and those residing in shelters.

The main symptom of this disease is the presence of tumors which are usually located in the genitals of both sexes, as well as the nasal and oral cavities. While tumor spread is uncommon, it can occur without a genital tumor being present. Locations can include:

Tumors can appear as small papules or nodules, and over time, they can progress into a cauliflower-like, multi-nodular, or multi-lobulated appearance. They can range in size from 5 mm to 15 cm in diameter, and are usually firm. Tumors often ulcerate, become inflamed, and bleed easily. Other signs associated with these tumors include:

Unlike other tumors that develop from the host’s own cells, TVT is clonal in origin, and is essentially a transplant of living cancer cells from one dog to another. While the original cell may have been a histiocyte, a type of white blood cell, TVT cells have a different number of chromosomes that do not come from the host dog.  

TVT is transferred by:

Most often, the presence of a tumor in the genital region will prompt a veterinary visit. A physical examination may include a digital vaginal examination in females, and possibly a vaginoscopy, as tumors can grow inside the vagina and be hard to see. A diagnosis is based on symptoms, the presence of tumors, and the results of testing.

A urinalysis is performed, along with blood tests that include a CBC and serum analysis, all of which can rule out the presence of parasites that can cause many of the same symptoms. It can also reveal abnormalities that can point to organs that may be affected. Tissue samples can be collected by a fine needle aspiration, surgical excision, or punch biopsy, and are analyzed to discover the nature and type of tumor your dog has. This tumor has a characteristic appearance which can help to diagnose this particular type of cancer.  

If it is suspected that internal organs may be affected, imaging techniques such as X-rays and ultrasounds can be used to reveal internal masses and organ damage.

In some dogs, tumors can trigger an immunologic response that can result in spontaneous regression of the tumor. Often, tumors will grow rapidly, then remain at a certain size before regression can occur, after which your dog may be resistant to a future implantation of TVT cells.

In dogs whose immune systems are unable to properly respond, tumors will continue to grow and spread into other areas, and will need to be treated. Surgical excision of small or localized tumors can be effective, but may not be the best choice when external genitalia is affected, and also carries the risk of tumor implantation into surgical wounds from instruments and gloves that have become contaminated. Recurrence has been seen to occur even in successful tumor removal. Most often, surgery is followed by other therapies.

Radiation therapy has been effective, while chemotherapy remains the best way to treat these tumors. Various chemotherapy medications can be administered over the course of 4 to 6 weeks, and can result in complete remission. 

Another experimental method is the use of biotherapy, or biologic response modifiers. These are antigen vaccines, growth factors, or immunomodulators that change the tumor’s relationship with the host by affecting the tumor directly, or it’s environment.

Recovery from TVT can be good. Some tumors can spontaneously regress without treatment. Tumors that require treatment have a 90% chance of complete remission with the right therapies. Recurrence of the tumors can occur, but is much less likely with the use of radiation or chemotherapy. If the tumors have spread to internal organs, there may be further complications that can compromise recovery. If this is the case with your dog, your veterinarian will discuss your dog’s chances of recovery based on his particular case.  

After any surgery, you may need to monitor wounds and change bandages, as well as administer any post-surgery medications. Watch for swelling or bleeding at the surgery site, and report them to your vet. You may need to take your dog in for scheduled weekly treatments. 

TVT is spread through sexual or direct contact with tumors. Preventing this disease may be difficult if you do not know the health status of your dog, or other dogs he may come into contact with. If you know your dog has TVT, prevent him from having any physical contact with other dogs, including licking, biting, rubbing, or mating. Be sure to wash your own hands after contact with your dog to prevent spreading the living cells to other dogs as well.