Sticker’s sarcoma

The Sticker’s sarcoma – also known as TVT (transmissible venereal tumour) or contagious venereal tumour – is a genuine rarity among cancers in dogs. What makes it so special: It is not a virus or pathogen that is passed on, but the tumour cells themselves migrate from one animal to another. This sounds almost surreal, but is well documented biologically. The tumour is typically transmitted during mating, less commonly through licking or sniffing in the genital area.

What is a Sticker’s sarcoma?

A Sticker’s sarcoma is a malignant (cancerous) tumour that spreads in a way that is almost unique in oncology: The tumour cells themselves are transferred directly to the new host and begin to grow there – entirely without an intermediate stage involving a pathogen. TVT therefore belongs to a handful of known cancers worldwide that are actually transmissible from individual to individual.

The external genital organs are primarily affected. If contact occurs through licking or sniffing, the cells can also take hold in the face, nose or mouth – this is something to bear in mind if you take in a dog from countries with a high stray population.

Transmission routes of Sticker’s sarcoma

By far the most common route of transmission is direct sexual contact. During mating, tumour cells pass from the infected animal to the mucous membrane of the other dog – a brief moment is sufficient for this. In addition, there are two further routes:

1. Licking or sniffing: Dogs that intensively sniff or lick infected dogs in the genital area risk tumour cells reaching their nasal or oral mucosa.
2. Close physical contact with infected areas: This route is rare but documented – particularly with wounds or severely abraded mucous membranes.

In Switzerland, TVT occurs worldwide, but more frequently in areas where many dogs are unneutered and roam freely – i.e. in parts of Southern Europe, Latin America or Asia. Anyone adopting a dog from such regions should keep this in mind.

Symptoms of Transmissible Venereal Tumour in Dogs

The most striking sign is cauliflower-shaped tumour masses in the genital area – soft, easily injured and often bleeding. They can occur on the external genitalia, in the vagina, prepuce or penis. Possible in both sexes. Further symptoms may occur depending on the spread of the tumour:

1. Swollen or bleeding tumours: The tumours are often red and ulcerated, meaning they bleed easily. This may manifest as blood in the urine or discharge.
2. Genital discharge: Both male and female dogs can exhibit discharge from the vagina or prepuce, which is often bloody or purulent due to tumour growths.
3. Difficulty urinating or mating behaviour: In advanced cases, dogs may have difficulty urinating or attempting to mate, as the tumours block the urethra or genital organs.
4. Tumours in other locations: If the dog licks or sniffs infected areas, tumours may also appear in the mouth, on the lips, nose or face.
5. General weakness: In advanced cases, when the tumour has metastasised or spread to other parts of the body, the dog may show general weakness, loss of appetite and lethargy.

Diagnosis of Transmissible Venereal Tumour

The diagnosis is based on a combination of clinical symptoms and diagnostic tests:

1. Clinical examination: The vet examines the genital area and other affected body parts for bleeding, cauliflower-like tumours.
2. Fine-needle aspiration (FNA): To confirm the tumour, a fine-needle aspiration is often performed. A small sample of tumour cells is taken and examined microscopically. The cells of the transmissible venereal tumour have a characteristic appearance that allows for diagnosis.
3. Histopathology: In some cases, a tissue biopsy of the tumour may be taken to confirm the diagnosis. This is often used to determine the degree of malignancy and the extent of tumour infiltration.
4. Imaging techniques: In advanced cases or if metastasis is suspected, X-rays or ultrasound examinations may be performed to check whether the tumour has spread to other parts of the body.

Treatment of Transmissible Venereal Tumour

TVT belongs to those cancer diagnoses where the news brings at least a glimmer of hope: Most dogs respond well to therapy. Depending on the location and extent of the tumour, various approaches are used:

Chemotherapy:

• Vincristine is the treatment of choice. It is administered intravenously and leads to complete regression in a large proportion of patients. Usually, 3 to 6 sessions are necessary – although many dogs already show significant tumour shrinkage after the first treatments.
• The response rate is remarkably high; this makes vincristine the standard therapy for TVT.

Radiotherapy:

• For dogs in whom chemotherapy does not work or surgery is not an option, radiotherapy can be an effective alternative. It is used less frequently but can certainly be successful.

Surgery:

• If the tumour is easily accessible and still locally confined, it can be surgically removed. However, there is a risk that individual tumour cells will remain and grow again – therefore, chemotherapy or radiotherapy often follows surgery.

Immunotherapy:

• In certain cases, the dog’s immune system is specifically stimulated to attack remaining tumour cells. This approach is currently less widespread but is an active field of research.

Prognosis for Transmissible Venereal Tumour

If the tumour is detected early, the outlook is good. Complete regression is not uncommon with timely treatment, and relapses remain the exception after successful therapy.

• Early treatment: The sooner you act, the better. If the tumour is left untreated, it can grow, bleed repeatedly and – in advanced cases – also spread (metastasise). This considerably complicates therapy.
• Advanced cases: Even if metastases are already present, chemotherapy can slow growth and noticeably improve the dog’s quality of life – the prognosis is then more cautious, but not hopeless.

Prevention of Transmissible Venereal Tumour

A hundred percent protection does not exist, but there is much that can be done:

1. Neutering or sterilisation: Neutered dogs do not have sexual contact – thus removing the most important route of transmission. This significantly reduces the risk.
2. No contact with infected dogs: If a dog shows symptoms suggesting TVT, it should be kept away from contact with other animals until a diagnosis has been made and treatment initiated.
3. Regular veterinary check-ups:: Having your dog examined routinely increases the chance of detecting a tumour early – and thus precisely at the stage where treatment is most effective.

Conclusion

The Sticker sarcoma (TVT) is biologically one of the most unusual tumours – a cancer that behaves like an infectious disease. Despite its malignant nature, treatment is successful in many cases, largely thanks to vincristin chemotherapy. Regularly having your dog checked, opting for neutering, and avoiding contact with potentially infected animals are the right steps – for your own pet as well as for others.