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

TUMORS AND CANCERS • 543
sporting breeds, Poodles, Boston
Terriers, and Dachshunds. Multiple
tumors are common. If a bitch has one
tumor, she is three times more likely
to have or develop a second tumor.
The principal sign is a painless lump
or mass. Most lumps occur in the larger
glands closest to the groin. A mass may
be large or small, with boundaries that
are distinct or indefinite. Some lumps
are freely moveable, while others
adhere to the overlying skin or underlying
muscle. Occasionally, the mass
ulcerates the skin and bleeds.
Inflammatory cancer is a rapidly
progressive neoplasm that spreads A bitch with mammary cancer.
throughout the chain of mammary
glands and into surrounding skin and fat. Death usually comes in a matter of
weeks. Inflammatory cancer may be difficult to distinguish from acute septic
mastitis (which is discussed on page 484).
Malignant tumors spread widely, primarily to the pelvic lymph nodes and
lungs. Before embarking on treatment, a chest X-ray should be taken to rule
out lung metastases, present in 30 percent of these cancers. Ultrasonography is
useful in determining whether the pelvic lymph nodes are involved. Biopsy of
the tumor may not be necessary if surgical removal is contemplated.
Inflammatory cancer, however, must be biopsied, because there is little to be
gained in attempting aggressive treatment in these tumors.
Treatment: Removing the lump with adequate margins of normal tissue is
the treatment of choice for all mammary tumors, whether benign or malignant.
How much tissue will be removed depends on the size and location of
the tumor. Removing a small tumor with a rim of normal tissue is called a
lumpectomy. A simple mastectomy is the removal of the entire mammary
gland. A complete unilateral mastectomy is the removal of all five mammary
glands on one side of the body. The inguinal lymph nodes are often included
in a unilateral mastectomy. A specimen is then submitted to a pathologist for
a tissue diagnosis to determine the prognosis.
The success rate of surgery depends on the biological potential and the size of
the tumor. Benign tumors are cured. Bitches with small malignant tumors less
than 1 inch (25cm) across have favorable cure rates. Those with large, aggressive
tumors are more likely to have metastatic disease and a poor prognosis.
The addition of chemotherapy, immunotherapy, and complete ovariohysterectomy
does not improve cure rates, although chemotherapy may offer
some relief in bitches with advanced cancers that cannot be surgically
excised.