Understanding Bone Cancer in Dogs

You don't want to think about your dog getting sick, but staying informed can help you navigate even the most difficult situations — including cancer. Osteosarcoma is the most common bone cancer in dogs. The Morris Animal Foundation reports that more than 10,000 cases occur each year, accounting for more than 85% of all canine bone cancer diagnoses. Knowing the signs of bone cancer in dogs is an important part of getting your pal help sooner.

What Is Bone Cancer?

Osteosarcoma is a cancer of osteoblasts, which are bone stem cells. A malignant cancer, osteosarcoma spreads to other parts of the body, including the lungs, lymph nodes, skin, liver, kidney and other bones. While osteosarcoma can affect any bone in the body, it most commonly attacks the long bones of the legs, usually near the ends of the bones, and often appears around the wrists and knees. Osteosarcoma can occur in dogs of any age or breed, but older dogs and large breeds are more affected. Golden retrievers, Rottweilers, Irish wolfhounds, Great Danes, boxers, Irish setters, greyhounds, Doberman pinschers and German shepherds appear to be at increased risk for this disease.

The cause of osteosarcoma is likely genetic. Other contributing factors can include chronic inflammation associated with metal implants and prior radiation therapy. Based on a study in Frontiers in Veterinary Science, early spaying or neutering in certain breeds is another possible risk factor. While osteosarcoma is the most common type of bone cancer in dogs, other bone cancers include fibrosarcoma and chondrosarcoma. Cancer can also spread from other organs, including the prostate and mammary glands, to your dog's bones.

Signs

The most common, and often first noticed, signs of bone cancer in dogs are limping and pain in the affected leg. The degree of limping and pain can range from mild lameness to refusing to put any weight on the leg. There may also be a firm, painful swelling on the bone that has cancer. Because cancer weakens the bone, some dogs develop a pathological fracture of the affected bone, which causes sudden severe limping and pain.

Diagnosis

Your veterinarian is key in determining if your dog has any type of bone disease. Because the signs of bone cancer in dogs can mimic other conditions, like fungal or bacterial infections of the bone, they'll need to run some tests to identify what's causing your dog's pain. Preliminary testing typically includes laboratory tests on blood and urine and radiographs (X-rays) of your dog's bone. Your vet will usually also take radiographs of your dog's chest to check for any sign of metastatic cancer in the lungs.

If your vet suspects bone cancer, they'll likely recommend additional testing that can include nuclear bone scans, a bone biopsy or a bone aspiration. These procedures are done under sedation or anesthesia. A bone aspiration is a relatively noninvasive procedure; your vet will insert a needle into the bone to withdraw cells to be analyzed in a laboratory. A bone biopsy is more invasive, but it's the best way to diagnose bone cancer as it's highly accurate. With either procedure, your dog will be asleep and will receive pain medication so they don't feel any discomfort.