There are many diagnoses that inflict fear upon pet owners that also greatly compromises a pet’s quality of life.

Cancer likely tops of the list of such concerning health problems.

Osteosarcoma is one of the worst types of cancer affecting pets due to the aggressive nature of the disease and the significant pain that it causes affected patients.

What is Canine & Feline Osteosarcoma

Osteosarcoma is malignant cancer of bone cells. Malignant cancers are generally considered to have a worse prognosis than benign cancers due to the tendency to be both locally invasive and have a high potential for metastasis (spreading to other body systems). Benign cancers typically have a better prognosis, as they are less likely to metastasize but can be locally invasive.

Osteosarcoma is the most common bone cancer affecting dogs. Other cancers affect bone, either by having origin in bone or spreading there. Osteoma is a benign tumor of bone cells that stays localized but can still cause pain, swelling, and other related problems. Malignant cancers of glandular tissues, such as adenocarcinoma, can have origin in the liver, kidney, thyroid, prostate, mammary and other tissues and metastasize to bone.

Any bone in the body can be affected by osteosarcoma, but long bones like the humerus (bicep bone) and femur (thigh bone) are common sites of diagnosis. Such bones are part of the appendicular skeleton, along with the scapula (shoulder blade), clavicle (collar bone, just a vestigial bone in dogs and cates), radius and ulna (forelimb bones), and tibia and fibula (shin bones). The bones of ribs, skull, sternum (breastbone), and vertebrae (backbone) make up the axial skeleton.

According to Malignant Bone Tumors in the Dog, in an expansive study of 1,215 cases, 82% of osteosarcomas involve the appendicular skeleton, while 18% affected the appendicular skeleton. There is also a trend for osteosarcoma to occur away from the elbow (higher up on the humerus) and near the knee (further down the femur from the hip). The distal radius (portion closer to the knee) and the proximal humerus (portion closer to the shoulder) are respectively the first and second most-common sites where canine osteosarcoma is diagnosed.

What are the Causes of Osteosarcoma in Dogs and Cats

There are no known causes of osteosarcoma, but there are correlations in certain dog breeds (and their mixes), sizes and ages.

Large and giant-breed dogs like the Boxer, Doberman Pinscher, Great Dane, Irish Setter, Labrador Retriever, Mastiff, Rottweiler, Saint Bernard, Scottish Deerhound, and others are well-documented as susceptible breeds. The mixes of these breeds may have similar tendency to develop osteosarcoma.

Some breeds have a trend for males or females to be more commonly-affected by osteosarcoma. The male German Shepherd, Labrador Retriever, and Old English Sheep Dog show a greater indigence of the disease. The female Great Dane, Rottweiler, and Saint Bernard have a greater tendency for osteosarcoma.
Large and giant-sized dogs are more known to have osteosarcoma than small and medium-sized dogs. Giant-sized dogs, which weigh more than 90 pounds, account for 29% of the cases of osteosarcoma. Large-sized dogs, with weights ranging from 60 to 90 pounds, make up 55% of osteosarcoma cases. Medium-sized dogs, having weight ranges from 30 to 60 pounds, comprise of 11% of osteosarcoma cases. Small-sized dogs weighing less than 30 pounds are the luckiest of the bunch as they only account for 5% of osteosarcoma cases.

Adult and senior dogs develop osteosarcoma more commonly than juveniles (puppies). Malignant Bone Tumors in the Dog indicates “the average age of onset of osteosarcoma in the dog is about 7 and 1/2 years, with a range of 1 to 15 years.”

Dogs having had bone fractures may be at greater risk for osteosarcoma with those undergoing surgical repair with an implant (pin, plate, etc.) or external fixation.

Cats are less commonly affected by osteosarcoma than dogs, but the disease is the number one feline bone tumor. Fortunately for our feline friends osteosarcoma is less aggressive in their species than in canines.

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