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

X-rays can strongly suggest the disease, but a definitive diagnosis depends
on biopsy of the tumor. Osteosarcoma is an aggressive cancer that quickly
spreads to the lungs.
Chondrosarcoma is the second most common malignant bone tumor in
dogs. The average age of onset is 6 years. This tumor tends to involve the ribs,
nasal bones, and pelvis. It presents as a large, hard, painless swelling in an area
containing cartilage. This tumor also metastasizes to the lungs, but is less
aggressive than osteosarcoma.
Treatment: Malignant tumors such as osteosarcomas and chondrosarcomas
should be treated aggressively. Because these tumors metastasize to the
lungs, it is important to obtain a chest X-ray before recommending surgery.
The dog should have a complete physical examination, including a blood
count and a fine needle aspiration or biopsy of any enlarged lymph nodes.
Partial or complete amputation is the only effective treatment for osteosarcomas
of the limbs. Most dogs are able to get around well on three legs.
Although amputation rarely cures the cancer, it does relieve pain and
improves the quality of life. The amputation should be performed at least one
joint above the involved bone. New surgical techniques that preserve the leg
are currently being done at some veterinary referral centers.
Chemotherapy in addition to amputation increases the survival time for
osteosarcoma, but not the cure rate. Radiation therapy may be considered if
the cancer is metastatic or far advanced, but is also not a cure. Osteosarcoma
of the mandible is treated with radiation therapy, to which it is moderately
responsive. Radiation is also used for palliation of pain.
Complete surgical removal of chondrosarcomas affords relief, but should
not be considered curative.
BENIGN BONE TUMORS
TUMORS AND CANCERS • 539
Osteomas are raised tumors composed of dense but otherwise normal bone.
They occur about the skull and face.
Osteochondromas, also called multiple cartilaginous exostoses, are bone
tumors that arise in young dogs from areas where cartilage grows prior to calcification.
Osteochondromas may be single or multiple and are found on the ribs, vertebrae,
pelvis, and extremities. There is a hereditary basis to osteochondromas.
A bone biopsy should be performed to determine the type of bone tumor,
unless the appearance on X-ray is conclusive.
Treatment: Benign tumors can be removed by local excision. The surgery
is needed when the growth impinges on structures such as nerves and tendons,
producing pain or causing inactivity. Surgical removal may also be indicated
for the sake of appearance.