These notes are provided to help you understand the diagnosis or possible diagnosis of cancer in your pet. For general information on cancer in pets ask for our handout "What is Cancer". Your veterinarian may suggest certain tests to help confirm or eliminate diagnosis, and to help assess treatment options and likely outcomes. Because individual situations and responses vary, and because cancers often behave unpredictably, science can only give us a guide. However, information and understanding about tumors and their treatment in animals is improving all the time.
This can be a very worrying time. If you have any questions please do not hesitate to ask your veterinarian.
What is a transmissible venereal tumor?
This is a common tumor, only found in dogs. It has a patchy worldwide distribution including parts of the Caribbean, USA, Southern Europe, Asia and Africa. It is transmitted by direct physical contact. It occurs in both sexes and may appear as multiple subcutaneous nodules on the genitalia, lips and other parts of the body.
What do we know about the cause?
Transmissible venereal tumor is a transplant of cancer cells. The cancer cells always have an abnormal number of chromosomes (59 instead of the normal canine 78). The original cell type is probably a histiocyte (part of the body's own immune system) but other types of white blood cells have also been suggested as the origin.
Why has my dog developed this cancer?
The cancer is transmitted by sexual contact or direct contact with the infected tumor (e.g. by licking). Therefore, an infected dog transmitted this tumor to your dog through direct contact.
Is this a common tumor?
These are common tumors of dogs in some parts of the world, particularly in stray dogs.
How will this cancer affect my dog?
The tumors are nodules, sometimes multilobulated, often found on the penis or vulva. Most ulcerate and bleed. The tumors may spread through the body, and the dog may develop many tumors in the skin.
The tumors grow rapidly at first and then remain static for a time. Eventually, they spontaneously regress due to antibody production by the immune system.
How is this cancer diagnosed?
Clinically, this tumor has a fairly typical appearance. Definitive diagnosis relies upon microscopic examination of tissue.
Your veterinarian may recommend one or more of various sampling techniques such as fine needle aspiration, punch biopsy and full excision. The sample will be prepared and examined by either cytology or histopathology. Cytology is the microscopic examination of cell samples obtained by aspiration techniques. This is useful for rapid or preliminary screening tests and can be diagnostic for these tumors. Histopathology is the microscopic examination of tissue samples that have been specially prepared and stained. Histopathology will give the most accurate diagnosis, prediction of behavior (prognosis) and assessment of whether the tumor has been fully removed. Histopathology also rules out other forms of cancer. Your veterinarian will submit the samples to a specialized laboratory for examination and diagnosis by a veterinary pathologist. Although the submitted piece of tissue may be a small part of the mass (biopsy) or the whole lump, only by examining the entire lump will the pathologist be able to indicate whether the cancer has been fully removed.
What types of treatment are available?
The most common treatment is surgical removal of the lump. Other treatments include chemotherapy and radiation. These are not suitable for all types of cancer and often have significant side effects. Some are only available at specialist centers.
Can this cancer disappear without treatment?
Yes. This cancer grows rapidly at first and then remains static before the dog's immune system produces specific antibodies that cause the tumor to spontaneously regress. Once the tumor regresses, that dog is then highly resistant to further tumor implantation.
How can I nurse my pet?
Preventing your pet from rubbing, scratching, licking or biting tumors will reduce itching, inflammation, ulceration, infection and bleeding. Any ulcerated area needs to be kept clean.
After surgery, the operation site needs to be kept clean and your pet should not be allowed to interfere with the site. Report any loss of sutures or significant swelling or bleeding to your veterinarian. If you require additional advice on post-surgical care, please ask.
How will I know if the cancer is permanently cured?
'Cured' has to be a guarded term in dealing with any cancer.
"In healthy dogs, spontaneous regression of a transmissible venereal tumor will indicate full cure."
The histopathology report will give your veterinarian the specific diagnosis that indicates how it is likely to behave. In healthy dogs, spontaneous regression of a transmissible venereal tumor will indicate full cure and the tumor is unlikely to regrow.
Are there any risks to my family or other pets?
Transmissible venereal tumor is transmitted from dog to dog. Preventing physical contact between your infected dog and others is essential. You should also wash your hands after handling your dog and disinfect anything that may be contaminated with living cells from your dog that could come into contact with other dogs. The tumor cannot be transmitted from dogs to other animal species or to people.
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