My veterinarian diagnosed my dog as having transmissible venereal tumor. What is this and what is the treatment and prognosis?
Transmissible venereal tumor (TVT) is a potentially cancerous growth that occurs most often in young, unneutered male and female dogs. Any breed may be affected. Female dogs are at a greater risk of developing TVT than male dogs. Feral and other dogs that come into frequent unrestricted contact with relatively large canine populations are at greatest risk. TVT is transmitted from an affected dog to a tumor-free dog by sexual contact. The primary tumor, which may arise as a single lump or as multiple masses, develops on the mucosa of the external genitalia. There are rare reports of tumors in the nasal and oral cavities associated with sniffing and licking behaviors. The transmission and behavior of TVT suggests a virus as a cause. However, to date no evidence to support this has been found.
These tumors may resemble small, pinkish to reddish cauliflower-textured nodules that may be firm or soft. They tend to bleed and may ulcerate. Definitive diagnosis of TVT requires some cellular sampling, with a fine-needle aspirate or biopsy. TVT may spread locally, but metastasis (distant spreading) to other tissues such as the skin, brain, and other organs occurs infrequently. Immunocompromised dogs may experience metastasis more frequently than dogs with a healthy immune system.
Spontaneous regression of TVT may occur. However, due to the chance of metastasis, especially in dogs whose immune status is unknown or not ascertainable, treatment is usually given. If the tumor is small and no metastasis has occurred, surgery may be curative if complete excision of the mass along with a zone of normal tissue is feasible. If the mass cannot be completely removed then chemotherapy or radiation may be used to treat the disease.
Several chemotherapy drugs have been used to treat TVT. Vincristine is perhaps the most effective agent against TVT. It is well tolerated by most dogs. Most dogs will need between two and six treatments for a complete remission to occur. Vincristine will eradicate both local and metastatic TVT; it is considered the treatment of choice for these tumors.
For dogs that cannot tolerate vincristine, radiation therapy may be very effective if no metastatic lesions exist.
Overall the prognosis for cure of TVT is good.
You may wish to speak with your doctor about referral to a veterinary oncologist for a discussion of the treatment options. Your veterinarian can help you locate a specialist in your area if you so desire.
12/07/00
