When we first hear that our dog might have bone cancer, we tend to beat ourselves up and wonder “how did we miss it?”

First, forgive yourself; the symptoms aren't always easily noticed.

Dog Bone Cancer Warning Signs

Sometimes bone cancer makes a sudden appearance as a lump in the leg, or in worst case scenario, as a pathologic fracture.

But in most dogs, bone cancer shows up slowly, often over a few months. A normally energetic dog may begin fatiguing after walking or playing. Some dogs will grumble when touched in a certain spot. A few dogs lose their appetite.

In older dogs, these symptoms are often mistaken for arthritis and in younger dogs, muscle sprains. Many vets opt to take the least scary (and most cost-effective) route to a diagnosis before even mentioning “bone cancer.” The dog is usually put on pain relief medicines to see if the problem goes away. Usually another round of tests aren't ordered until it becomes clear the medicines aren't helping.

Diagnosis: What to Expect

One of the first steps in diagnosing bone cancer is for your veterinarian to perform a complete physical exam, blood tests and x-rays. “In most cases, bone cancer can be diagnosed with an X-ray,” says Tripawd member and long-time supporter Dr. Pam Wiltzius of River Road Animal Hospital in Puyallup, Washington.

In the following video, Dr. Wiltzius explains the process of diagnosing canine bone cancer in dogs:

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Learn about amputation and what to expect with Tripawds eBook, "Three Legs & A Spare: A Canine Amputation Handbook."

When it comes to diagnosing bone cancer in dogs, Dr. Wiltzius shares these facts:

The most common locations where bone cancer appears are:

In the front legs, normally in the:

• distal radius (above the wrist joint)
• proximal humerus (upper arm bone, close to the shoulder blade)

Or, in a dog's rear legs, in the:

• Proximal tibia, or
• Distal femur (right above or below knee cap)

Once your vet takes the radiograph of the suspected area, she may consult with a specialist who can confirm whether or not a bone tumor is growing in the limb. If the bone tumor is abnormal in appearance, a biopsy may need to be taken.

There are two types of biopsies:

Fine Needle Aspirate

According to Dr. Wiltzius, a fine needle aspirate biopsy is fairly easy to perform. The veterinarian will inject a needle into the tumor area that's seen on the radiograph. Besides performing this biopsy on the leg, this type of biopsy can also be done when tumors are present on other parts of the skeleton, such as the skull or spine. After withdrawing the cells, the sample is sent to the lab and examined for cancer.

The disadvantage of a fine needle aspirate is that it can sometimes give a false-negative reading because the bone tumor may be too hard to reach with the needle.

Bone Biopsies

When a fine needle aspirate gives an inconclusive reading, a veterinarian will recommend a bone marrow biopsy. This is performed using a wider needle instrument that must reach through the cortex (center) of the bone, in order to get a large enough area to sample.

A bone biopsy can provide a definitive diagnosis, but it is extremely painful, requires recovery time and by taking such a large sample of bone, it can put the dog at risk of a pathological fracture. In most cases, this procedure is bypassed if a dog parent knows they will proceed with amputation no matter what the final diagnosis.

Where you live may play a role in whether or not your vet thinks its worthwhile to perform the bone biopsy procedure. For example, in areas where canine fungal diseases are prevalent (the U.S. Midwest and Southwest), vets may recommend it. This is because fungal infections can look like bone cancer on radiographs and cause similar symptoms. If your vet thinks a fungal disease is the issue, it might make more sense to take a bone biopsy prior to amputation, since fungal infections can be treated and don't require removing the leg.

Can a Biopsy Determine Survival Time?

Bone cancer biopsies help determine the grade of the cancer, but the grade won't determine survival time. According to Dr. Wiltzius, if a biopsy shows a high grade bone cancer, that doesn't necessarily mean that the dog won't live longer than dog with a low grade bone cancer. And the reverse is true; a dog with a low grade bone cancer might not last as long as a dog with a higher grade.

What does help determine the survival time is determining whether or not the cancer has spread to the lymph nodes. If cancer is found in the lymph node, it indicates that the cancer has spread beyond the leg and the dog's survival time may be shorter than most.

However, according to Dr. Wiltzius, just because there's cancer in the lymph node doesn't mean you shouldn't proceed with amputation. For most dogs who are suitable amputation candidates, the most humane thing that can be done for the dog is to remove the source of the horrible pain they are in as soon as possible and let them live out their days pain-free. Whether chemotherapy is chosen doesn't mattter at that point; all that matters is that the pain is gone.

Learn more about amputation and what to expect with Tripawds downloadable eBook, "Three Legs & A Spare: A Canine Amputation Handbook."

What About Lung Mets?

Most vets will take chest radiographs before amputation. If lung metastasis (cancer growths) aren't seen in the lungs, it's a good sign that the cancer hasn't aggressively spread throughout his body. But even with “clean” radiographs, remember that 90 percent of dogs already have cancer cells in their lungs at the time of surgery – it's just that the cells are too microscopic to be seen. Sadly, clean lungs at the time of surgery doesn't necessarily mean that cancer won't appear there later.

But what's important to understand before deciding to proceed with amputation, is that as long as your dog is not showing inward (or outward) signs of cancer, she will have a better chance of living a longer, healthier life and beating the bone cancer odds once the affected limb is removed. If a dog is a good candidate for life on three legs, just because a dog has a high grade tumor doesn't necessarily mean that amputation is a bad idea.

Many thanks to Dr. Pam Wiltzius for helping us bring this impawtant information to the Tripawds community. Stay tuned for more canine bone cancer and amputation surgery information.

More recommended reading: Colorado State University Animal Cancer Center: Bone Cancer in Dogs.