Reproductive Tract Tumors in Dogs (cont.)

Transmissible Venereal Tumors

An unusual neoplasm called transmissible venereal tumor occurs in both males and females. Tumor cells are transplanted from one dog to another, primarily during sexual contact, but also through licking, biting, and scratching. Transmissible venereal tumors tend to occur in free-roaming dogs, particularly those living in urban areas. They appear within seven days of contact exposure.

Transmissible venereal tumors are solitary or multiple tumors that usually appear as cauliflowerlike growths or as nodules on a stalk. The growths may be multinodular and/or ulcerated.

In females, transmissible venereal tumors develop in the vagina and on the vulva. In males, they occur on the penis. Other locations in both sexes include the skin of the perineum, face, mouth, nasal cavity, and limbs.

Transmissible venereal tumors are considered low-grade cancers. They do have the potential to metastasize, although this is rare.

Treatment: Chemotherapy is the recommended treatment. The drug of choice is vincristine, given weekly for three to six weeks. Radiation therapy is also highly effective; most dogs are cured after a single dose.

Surgery is not considered an effective treatment because it is associated with a high rate of local recurrence. Dogs and bitches not intended for breeding should be neutered or spayed.

Vaginal Tumors

The vaginal and vulvar areas are the most common sites for tumors of the female genital tract. These tumors tend to occur in older, sexually intact females, at an average age of 10 years. Benign tumors include leiomyomas, lipomas, and transmissible venereal tumors. They are often found on a narrow base or a long stalk.

Malignant tumors in this area are rare. They include leiomyosarcomas, squamous cell carcinomas, and mast cell tumors. Malignant tumors grow locally, infiltrate surrounding tissue, and become quite large. They rarely metastasize.

Signs include vaginal discharge or bleeding, a mass protruding through the vulvar lips, frequent urination, and excessive licking at the vulva. Large vaginal tumors can cause swelling and deformity of the perineum, block the birth canal, and cause problems in whelping. Note that a mass protruding through the vulva of a bitch in heat is most likely to be due to vaginal hyperplasia.

Treatment: Surgical removal with a margin of normal tissue is the treatment of choice. Recurrence may follow removal.