Osteosarcoma In Dogs And Cats

Most of us know someone who has suffered from cancer, but how can we spot it in our own pets? The best step all pet owners can take is learning about what cancer is, the symptoms to look for, and a few of the most common types of cancer we see in cats and dogs. This article focuses specifically on Osteosarcoma, or bone cancer, in both cats and dogs. 

What is Cancer?

Cancer is characterized by rapid and uncoordinated cell growth, often resulting in a large mass of tissue, or tumor. There are many types of cancer, and any cell type in the body could become cancerous from ongoing genetic damage. Cancers are classified based on the tissues (muscle, skin, bone, blood, organ) from which they arise. Just like in humans, cancer develops due to many factors and it is impossible to find just one cause for the disease. 

The clinical signs of cancer can unfortunately vary greatly, as it can affect any part of the body. A few common signs to look for include an unusual lump that continues to enlarge, unexplained weight loss, abnormal bleeding, unexplained vomiting or diarrhea, swollen lymph nodes, coughing, or lameness (a different or improper gait or posture). 

To treat cancer, veterinarians look first to surgically remove the tumor if possible. However, some tumors can be too large, numerous, or invasive to remove. Leukemia, or blood cancer, does not exhibit tumors at all. In these cases, options such as chemotherapy, immunotherapy, and radiation therapy are available at specialty centers. Unfortunately, a permanent cure is not the goal when a pet has cancer. Instead, the goal is to provide the best quality of life for your pet as long as possible. The most important thing to do after a cancer diagnosis is give your pet as much love as possible.

What is Osteosarcoma?

The root word “osteo-“ means bone, meaning Osteosarcoma is simply another word for bone cancer. Osteosarcomas are tumors that arise from the abnormal production of cells that create bone (osteoblasts) and cells that break down bone (osteoclasts). Most often, this affects the hind or front limbs, but osteosarcoma can also affect the jaw, hips, or pelvis. Extraskeletal osteosarcoma also is a possibility, affecting non-bony tissues such as the mammary glands, spleen, liver, and kidneys.

It occurs in dogs and less commonly cats, and often affects more large breed dogs over smaller breeds. For both species, this cancer is very painful. If your dog or cat has osteosarcoma of the limb, you may notice lameness/unusual gait and distinct swelling. They may be more lethargic, display a loss of appetite, and be reluctant to walk or play due to the pain on the bone. 

The most common areas for osteosarcomas in dogs are the upper arm (humerus) and upper leg (femur).In cats, osteosarcomas can also develop in the skull, pelvis, ribs, and vertebrae. Cats with osteosarcoma of the jaw may have swelling in the area, difficulty opening the mouth, excessive salivation, and reluctance to eat due to pain.

Diagnosing Osteosarcoma 

Most dogs and cats with osteosarcoma have lameness of a limb. In the area where the tumor is located, swelling and a higher temperature will be noted. To diagnose osteosarcoma, your veterinarian will take X-rays of the region. Osteosarcomas appear lytic — meaning pieces of the bone are missing — due to the loss of normal bone tissue. If the bone has weakened more, fractures can be present as well. 

Treatment for Osteosarcoma For dogs, osteosarcoma is extremely aggressive. Once diagnosed, about 90-95% of dogs will have micrometastases, meaning the cancer cells have already spread elsewhere in the body — even though they are not detectable yet. Osteosarcoma is less aggressive in cats, making micrometastases more rare. 

We often recommend searching for potential spread to other locations, called staging, for both dogs and cats. This may include blood work, urinalysis, examination of the lymph nodes, X rays of the lungs, and possibly an abdominal ultrasound. 

The primary goals are local tumor control and pain management, which typically involves amputation of the affected limb. This seems quite drastic for many pet owners, but cats and dogs often manage well after amputation. There are also treatments like palliative radiation that can help manage pain and temporarily slow tumor growth when amputation isn’t feasible.

At Harmony Vet Center, we can often help support the pet undergoing treatment. The types of support that we can offer include nutritional support, supplements, pain management and a variety of other alternative treatments. The needs of each patient are different and the approach we take will be specific to the needs of the individual. 

Regardless of the treatment plan decided upon with your veterinarian, pain management is the primary goal for all animals to ensure the best quality of life they can have. Discuss pre- and post-operative therapy and pain management plans with your veterinarian.