Signs of Osteosarcoma (Bone Cancer) in Dogs

Updated on September 14, 2016
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Adrienne is a former veterinary hospital assistant, certified dog trainer, behavior consultant, and author of "Brain Training for Dogs."

Lateral x-ray showing distal femur of a dog with osteosarcoma. Notice the large dark portion which is where the femur bone is being destroyed.
Lateral x-ray showing distal femur of a dog with osteosarcoma. Notice the large dark portion which is where the femur bone is being destroyed. | Source

Osteosarcoma is a word derived from "osteo" meaning bone and "sarcoma" meaning cancer. It's the cancer of the bones. It commonly strikes large dog breeds from their middle ages to senior years (even though there are cases affecting dogs as young as 2 years old!) It is uncommon in small dog breeds. Breeds particularly predisposed to osteosarcoma include Saint Bernards, Rottweilers, Great Danes, Golden Retrievers, Irish setters, Doberman Pinschers, and Labrador retrievers. On average it affects dogs in the 7-1/2 year range.

While it can affect basically any bone in the body, it typically affects the dog's legs ( 75-85% according to Mar Vista Vet) When a leg is affected, the condition is known as "appendicular osteosarcoma." Other predisposed areas include the ribs, vertebrae and skull, yet bone cancer in these areas are rare. In this article, we will mostly tackle bone cancer of the limbs.

Codman Triangle

Dog osteosarcoma Codman triangle
Dog osteosarcoma Codman triangle | Source

Signs of Osteosarcoma in Dogs

In osteosarcoma, the tumor originates from within the affected bone and destroys it from the inside out. The front limbs are most commonly affected, according to Vet Cancer Specialists. The cancer tends to form at or near the growth plates. The most common bones affected by osteosarcoma include, in order of preference: 1) distal radius 2) proximal humerus 3) distal ulna 4) distal femur 5) proximal tibia 6) distal tibia, and, 7) diaphyseal ulna. As vets often say, osteosarcoma in dogs is mostly seen “near the knee” and “away from the elbow.” See picture for exact locations of these bones. Sadly, dogs with osteosarcoma do not show symptoms in the early stages, which is why this condition is always discovered late and it is one of the most devastating diseases for dog owners to endure.

  • Progressive lameness

Owners often report limping in a forelimb or hindlimb without an evident cause and that does not get better with time. The lameness may wax and wane for some time, generally several weeks, but will not go away. Generally, the limping goes from intermittent to constant over the course of 1-3 months. It gets gradually worse as the cancer damages the bone and causes pain for the dog. However, some dogs may be quite stoic and not clearly manifest pain. The lameness is triggered by inflammation of the membrane that covers the outer surface of all bone, microfractures, or pathologic fractures. It's always a good idea to routinely observe your dog's gait so you can readily recognize signs of trouble.

Often, vets will try to treat the lameness symptomatically before running further tests. When the vet will do an x-ray, the affected bone may show signs of destruction (lysis) or abnormal growth, as seen in a typical sunburst pattern or Codman's triangle, signaling that the periosteum has been raised due to the tumor. In some cases, a biopsy of the bone may be needed to obtain a definitive diagnosis.

  • Swelling

As the cancer expands, it will cause swelling in the affected limb or shoulder area (see pictures). This swelling is therefore due the expansion of tumor into the surrounding soft tissues.The swollen area may appear hot to the touch and the dog may exhibit pain as the area is handled. However, as mentioned, the pain may not be that noticeable in stoic dogs. It's always a good idea to routinely touch your dog's legs and get familiar with how the bones and skin feel. If you ever feel a lump by the bone, or individualize a swollen joint, see your vet. If you are not sure, you can always use the other leg for comparison.

  • Fractures

The affected dog's bone typically become eroded and is replaced by tumorous bone which is friable and prone to fractures that do not heal. Typically, the dog owner reports that the dog was playing one minute, and yelping the next when the fracture occurred. The fracture in this case is known as "a pathologic fracture" since it affects tumorous bone. X-rays of the bones may show eroded bones, the typical sunburst pattern or Codman triangle, which provide a diagnosis.

  • Difficulty breathing/Coughing

Sadly by the time the cancer is discovered, almost 90% of cases have already metastasized, according to the American Kennel Club's Canine Health Foundation. Microscopic metastasis is therefore often present at the time of diagnosis.The most common area of metastasis are the lungs.This explains why your vet will often do a chest x-ray (2 lateral views and a ventrodorsal one) as well to check if the cancer has spread. However, it appears that fewer than 10% of dogs show evidence of lung metastasis at the time of diagnosis, according to Vet Cancer Specialists. A CT scan of the lungs may be more effective than x-rays in identifying the initial small metastatic lesions. While metastasis to the lungs is the most common, other affected sites may be the liver, kidneys, amputation stump, and, nearby bones, even though rare.

  • Behavior Changes

When dealing with cancer, the dog's immune system is put to test which results in lethargy and tiredness. The dog may weaken and appear less interested in food. Pain may cause walks or play to be too much for the dog. Affected dogs may sleep more, appear tired and pain may put a big toll in the dog's quality of life. The dog with bone cancer may also appear grumpy and may not want to be touched. Amputation may make the pain more bearable, but will not cure the disease.

Disclaimer: this article is not a substitute for professional veterinary advice. If your dog is limping, has swelling or other symptoms please see your vet promptly.

Occurrence of Bone Cancer in Dog Front Legs (in order of preference)

Edited to show frequent bone cancer locations in dogs.
Edited to show frequent bone cancer locations in dogs. | Source

Did you know?

About 10,000 new cases of osteosarcoma are diagnosed in dogs each year!

A Grim Future for my Rotties?

Owning two Rottweilers puppies, I looked forward to getting them vaccinated and giving them a great head start in life by playing it safe and preventing any major disease or weakness by feeding the highest quality foods and having routine check ups all their lives. However, once six months old, I asked the vet when the best age was to get them neutered and spayed and her answer was as early as possible. I trusted my vet, and vets in general because I always thought of all the years of education they undergo. So I had them altered immediately a week thereafter. Big mistake...

Little did I know back then that there were studies out there suggesting that large breed dogs spayed and neutered too early in life, were shown to be prone to osteosarcoma as they approached their middle to senior years! Actual studies have reported that chances of osteosarcoma decreased when Rotties were spayed and neutered once they were at least one year old. More precisely, the studies reported that male and female dogs spayed and neutered before 1 year of age had a higher incidence (1 in 4 chance ) of developing osteosarcoma! This suggests that sex hormones play a role in the the inhibition of bone cancer. Studies are currently underway to investigate the genetic susceptibility to osteosarcoma in Rottweilers and other breeds by fundings organized by the Canine Health Foundation and the Morris Animal Foundation.

Owning two rotties, respectively spayed and neutered before 1 year of age, seems to make statistics quite scary for their future. So I have learned my hard lesson, and now I am always worried sick that one day or another one of my Rotts will start limping and showing signs of this devastating condition.

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Questions & Answers


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      • habee profile image

        Holle Abee 7 weeks ago from Georgia

        Adrienne, thank you for your kind words.

      • alexadry profile image

        Adrienne Janet Farricelli 7 weeks ago from USA

        Holle Abee, so sorry for your loss. Bone cancer is so mean. Rotties are also prone to it and so every time mine limp, I get worried and get them x-rayed to play it safe. Again, so sorry.

      • habee profile image

        Holle Abee 8 weeks ago from Georgia

        Had to have my beloved Dane put down due to osteosarcoma. He was 8. The tumor was on his wrist. He never limped much, but he did have a slight decrease in appetite. Great Danes are prone to this terrible disease.

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        Atlas123456 6 months ago

        Taking my Saint Bernard to the vet this Saturday. He has a lot of these symptoms. Not wanting to eat unless I add chicken to his food, seems very stiff when getting up, favors one rear leg over the other, walks slowly, sleeps more than usual. I hope it isn't cancer, he's only 6 years old. Just the thought is absolutely devastating.

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        Tina 10 months ago

        I just took one of my Rottie's yesterday to a new vet for limping and they did a 3D scan. They are sending it out for a second opinion but it doesn't look good for my sweet, sweet Maddie. Both her and her sister were spayed at 6 months by the advice of our previous vet. So sad to think my girl who has never been sick is going to have to be put down at the age of 8. I am already dealing with her sister having two disk issues and severe arthritis. Cancer sucks and to think of precious Maddie having it is devastating.

      • alexadry profile image

        Adrienne Janet Farricelli 12 months ago from USA

        Sarah, sending prayers your way.

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        Sarah 12 months ago

        My almost 14yr old 70lb large black lab Shepard mix started limping after being trampled by my other dog so I took her to the vet. We thought maybe a ligament or muscle (because X-rays showed no breaks) but after a week and a half her leg quickly got bigger and swollen.

        I took her back to the vet today and I could tell when the vet tech left us in the room with just the dr, there was bad news. She had suspected osteosarcoma previously. She gave me antibiotics anyways because I'm hopeful it's just infected from a sore on her elbow. She is also taking tramadol and carprophen. I have had her since she was 8weeks and I was 15yrs, I'm heart broken.

      • alexadry profile image

        Adrienne Janet Farricelli 14 months ago from USA

        Benjamin, I am so sorry, bone cancer is so devastating.

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        Benjamin 14 months ago

        Im saying goodbye to my best friend of 9 and 1/2 years this weekend. We finally found out this past Monday that she had bone cancer on her left front leg at the wrist joint.

      • alexadry profile image

        Adrienne Janet Farricelli 15 months ago from USA

        NikkiB, so sorry to hear about your dog's bone cancer, it's really a devastating disease, to answer your question, there are some pet owners using it and indeed there is a Facebook page you may want join where people share their experiences.

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        NikkiB 15 months ago

        We adopted a 10 yo sharpei mix in mid-November, 2016. He was dx'd with osteosarcoma on Dec. 29, 2016. He'd become such a wonderful part of our family in those 6 weeks. We were told he had maybe 3 months. He is now on tramadol. He still eats well, he seems pretty happy other than limping. His tumor is on the humerus. In just three short weeks, we've already noted the progression of his tumor. It went from a "halved" golf ball size to a halved racquetball size in that short time. As long as he can get around, and wants to eat (and go for walks still!), we'll keep things as normal as possible.

        I'm really curious- does anyone have any positive experience using cbd oil supplementation? I was hoping it might slow the progression down and ease his pain. Thanks!

      • alexadry profile image

        Adrienne Janet Farricelli 17 months ago from USA

        Rebecca, I am so sorry to hear about your dog. Just last week a client of mine had her dog diagnosed with bone cancer of the jaw, the symptoms were mimicking a bad tooth and then the x-rays showed the extent of the damage to the bone. Keeping you in my thoughts.

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        Rebecca Williams 17 months ago

        My 8 year old chocolate lab was just diagnosed. He started having seizures. After a MRI and biopsy it was confirmed. The growth is in his skull and growing toward his brain. Anti seizure meds are helping with the seizures, just don't know how much time he has. Very cruel disease.

      • alexadry profile image

        Adrienne Janet Farricelli 19 months ago from USA

        Karen, did your vet take x-rays of the leg and lungs? what about consulting with a veterinary oncologist?

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        Karen Phillips 19 months ago

        I'm pretty certain my beautiful gsd x has osteosarcoma in her back right leg. She was seem by a vet last week and we were told to go home and decide what course of action we would like to take. Amputation is not an option and it seems that putting her to sleep is going to be the result we are dreading. My heart is breaking at the thought of her leaving but more that she is and will continue to suffer. I'm looking at her sleeping peacefully at my feet and hoping that I can do what is right and best for her.

      • alexadry profile image

        Adrienne Janet Farricelli 2 years ago from USA

        Talk to your vet about amputation and chemo, I know many dogs who live happily more months or even years.

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        Debby 2 years ago

        Our Great Pyrenees dog Casper is being biopsy tested for osteosarcoma tomorrow. He is 7 yrs old. The sweetest guy you could imagine. It's pretty likely this will be bad news. All the signs are present. We just want to confirm our worst fears before we put him down. We had originally taken Casper to the vet because we thought he had a sprained leg. No clue this is what was going on. This is a very aggressive and quick cancer. Don't wait to take your large dog to the vet when he is limping. Get it checked out.

      • DDE profile image

        Devika Primić 3 years ago from Dubrovnik, Croatia

        A well-informed hub on this topic. Always something more from your writing about dogs and about their health issues.

      • alexadry profile image

        Adrienne Janet Farricelli 3 years ago from USA

        Goatfury, there are some cancers that can be treated at the early stages, or at least, managed for quite some time, but osteosarcoma is one of meanest, most painful, and with a poor prognosis and signs showing up when it's too late:(

      • alexadry profile image

        Adrienne Janet Farricelli 3 years ago from USA

        Heidithorne, that must have been devastating, what an awful disease. I hope those funded studies and research finally help shed some light on this cancer.

      • goatfury profile image

        Andrew Smith 3 years ago from Richmond, VA

        Thanks for writing this. I really hope none of my dogs end up with osteosarcoma!

      • heidithorne profile image

        Heidi Thorne 3 years ago from Chicago Area

        We've had mutiple goldens with cancer. One of the most heartbreaking was my 2-year old who had osteosarcoma lodged behind his brain which then progressed into lymphoma. He had dramatic and early deterioration of his teeth. This also emphasizes the importance of canine dental monitoring and care to identify other health issues. Thanks for sharing the information!

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        Adry 3 years ago

        According to Pet Education: " Most osteosarcomas develop on the limbs of dogs below the elbow or near the knee". There are some that develop swelling in the shoulder area as you can see in the picture links, but hopefully in your dog's case it's something else. Definitively something that should be checked out by your vet though.

      • Just Ask Susan profile image

        Susan Zutautas 3 years ago from Ontario, Canada

        My Newfoundland dog Bruce is 7 and will be 8 in March. He is not fixed. His right front leg where his elbow is, is quite swollen. He doesn't seem to be experiencing any pain except he is limping really bad. He started this about a week ago. After reading your hub I'm really worried. We had thought that maybe he had just pulled a muscle as he has had this happen a number of times in his life. I now think it would be best for us to take him to the vet.