Dog Owner's Home Veterinary Handbook.pdf - Mr. Walnuts

542 •DOG OWNER’S HOME VETERINARY HANDBOOK
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 (see
page 460).
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.
Papillary adenoma is a benign tumor that may arise simultaneously in both
ovaries. A malignant variety, called papillary adenocarcinoma, is the most
common ovarian cancer in bitches. These tumors spread throughout the
abdominal cavity and are associated with ascites.
Granulosa cell tumors can also become quite large. Some secrete estrogen,
producing signs of hyperestrogenism with abnormal heat cycles, enlargement
of the vulva, and a greasy skin and coat.
Other tumors of the ovaries also occur. Ovarian cysts, which are not true
tumors, are discussed in Abnormal Estrous Cycles, page 449.
Abdominal ultrasonography is particularly helpful in determining the size,
structure, and location of ovarian tumors. Finding ascites and masses in the
abdominal cavity suggests malignancy.
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 in remission.
MAMMARY GLAND (BREAST) TUMORS
The mammary glands in female dogs vary in number and can be determined
by counting the nipples. The typical bitch has 10 mammary glands, five on
each side of the midline, beginning on the chest and extending to the groin.
The largest glands are located near the groin.
Mammary gland tumors are the most common tumors in dogs. In fact,
among unspayed females the risk of a mammary tumor is 26 percent. This is
three times the risk of breast tumors in women. Most mammary gland tumors
occur in bitches over 6 years of age (the average age is 10). Forty-five percent
are cancerous and 55 percent are benign. An increased incidence occurs in