What is this tumor?
This is a common tumor, only found in dogs. It has a patchy world-wide distribution including parts of the Caribbean, USA, Southern Europe, Asia and Africa. It is transmitted by physical transplantation. 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?
The reason why a particular pet may develop this, or any cancer, is not straightforward. Cancer is often seemingly the culmination of a series of circumstances that come together for the unfortunate individual.
The 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).
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 on the penis or vulva. Most ulcerate and bleed. The cancers may spread through the body with 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.
Various degrees of surgical sampling may be needed such as needle aspiration, punch biopsy and full excision. Cytology is the microscopic examination of cell samples. This is used for rapid or preliminary tests and can be diagnostic for these tumors. The most accurate diagnosis, prediction of behavior (prognosis) and a microscopic assessment of whether the tumor has been fully removed rely on microscopic examination of tissue (histopathology). This is done at a specialized laboratory by a veterinary pathologist. The piece of tissue may be a small part of the mass (biopsy) or the whole lump but only examination of the whole lump will indicate whether the cancer has been fully removed. Histopathology also rules out other cancers.
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 causes the tumor to spontaneously regress. That dog is then highly resistant to further tumor implantation.
How can I nurse my dog?
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 similarly needs to be kept clean and your pet should not be allowed to interfere with the site. Any loss of sutures or significant swelling or bleeding should be reported 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.
Histopathology will give your veterinarian the specific diagnosis that indicates how it is likely to behave. In healthy dogs, spontaneous regression will indicate full cure and the tumor is unlikely to regrow.
Are there any risks to my family or other pets?
This is a tumor that can be 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 and then come into contact with other dogs. The tumor cannot be transmitted from dogs to other species or to people.
Based on material written by Joan Rest, BVSc, PhD, MRCPath, MRCVS. and modified with permission from Lifelearn Inc.
© Copyright 2004 Lifelearn Inc.
