Reproductive Tract Tumors in Dogs
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
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.
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
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
Treatment: Surgical removal with a margin of normal tissue is the treatment
of choice. Recurrence may follow removal.
Tumors of the Ovaries
Ovarian tumors are uncommon. Most cause no symptoms and are found
incidentally during a spay operation. Occasionally, a tumor becomes large
enough to produce a visible or palpable swelling in the abdomen.
Treatment: Removal of the ovaries by ovariohysterectomy (spaying) cures
benign tumors. The cure rate for malignant tumors is about 50 percent. The
addition of chemotherapy for metastatic tumors may extend the time the dog is