Bone cancer in dogs generally refers to osteosarcoma, although other cancerous tumors also occur. Most often, osteosarcoma develops in the long bones of the legs of larger dogs. X-rays can be used, both in the diagnosis of this tumor, and in the treatment as radiation therapy.
Malignant vs. Benign Bone Tumors
There are different types of canine bone tumors.
A tumor results from uncontrolled cell growth. Benign bone tumors generally grow locally, but do not spread to remote areas of the body, and are not called cancer. Malignant bone tumors are those that can metastasize, spreading to remote locations within the body. Bone and associated tissues such as cartilage are called connective tissue. Tumors that develop from connective tissue, or from muscle tissue, are called sarcomas.
Types of Malignant Bone Tumors in Dogs
Osteosarcoma, the most common malignant bone tumor, is produced by cells that are cousins of the cells that normally produce the calcified matrix that makes bones hard. However, there are other malignant canine bone tumors.
Other types of Malignant Canine Bone Tumors
Different types of bone cancer are more likely to develop in different types of bone.
Chondrosarcoma is a tumor of cartilage cells. In contrast to osteosarcoma, it occurs mostly in flat bones and ribs, as opposed to long bones. Other sarcomas can occur in other areas of the bone, such as the linings of joint capsules. Carcinomas, malignant tumors that develop from epithelial cells, also can occur in canine bone. Squamous cell carcinoma occurs in the periosteum, the outer layer of the bones.
X-rays in the Diagnosis of Canine Osteosarcoma
Treatment of canine osteosarcoma often involves amputation of the affected limb
X-rays are extremely useful in the diagnosis of osteosarcoma, because the tumor has a very distinct appearance compared to the surrounding healthy bone. One typical feature of osteosarcoma in an x-ray is known as a "sunburst pattern", appearing as a darkened area with lines radiating outward. X-rays reveal likely osteosarcoma; however, diagnosis should be confirmed by way of biopsy.
X-rays in the Treatment of Canine Bone Cancer
Surgery (particularly limb amputation) and chemotherapy are the mainstays of treatment for canine osteosarcoma, since radiation treatment using beams of x-rays have not been shown to cure the disease. Nevertheless, such radiation is used to shrink tumors that are too large for surgery, or as palliative treatment to make the dog more comfortable. Similar approaches are used in cases of chondrosarcoma.
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