Osteosarcoma in cats

Osteosarcoma is a type of bone cancer. It usually affects one of the limbs. It’s most commonly diagnosed at around 8-11 years of age. 

Osteosarcoma is a rare and painful cancer in cats. Early diagnosis increases your cat’s chances of survival.



What is osteosarcoma in cats?

  • An osteosarcoma is an irregular growth of bone-producing and bone-breaking cells.
  • This cancer usually appears primarily in the bones of the skull (head). But can develop in long bones in the hind leg, the front leg, and other bones of the body.
  • Rare cases arise in non-boney tissues, including under the skin on injection sites, mammary glands (teats), eyes and others.
  • This tumour can spread to other parts of the body (metastases), but it progresses much slower than in dogs.
  • The cause of this condition is unclear. There are very few tumours with a single known cause. Genetic and environmental factors (metallic implants, bone diseases) seem to play an important role.



What are the signs of osteosarcoma in cats?

You might notice some or all of the following in your cat.

In osteosarcoma of the skull:

  • Difficulty eating
  • Eye changes such as a swollen eye
  • Nose discharge
  • Face asymmetry
  • Changes in behaviour such as irritability or aggression

In osteosarcoma of the leg:

  • Limping
  • Swelling of the leg
  • Reluctancy to climb, walk, or play
  • Tiredness
  • Reduce appetite
  • Losing weight



Are some cats more at risk of osteosarcoma than others?

Cats of any age, gender or breed may be affected, although bone tumours predominantly affect middle- to old-aged cats.



How is osteosarcoma diagnosed in cats?

Diagnosis aims to not only investigate the primary tumour but also determine if the disease has spread elsewhere (metastasis). Your vet will:

  • Take a comprehensive history of your cat’s signs and any past bone injuries or surgeries.
  • Perform a hands-on examination.
  • Take Radiographs (x-rays): to check for a type of bone image that can be highly suspicious of the disease.
  • Run blood and urine tests
  • Perform:
    • FNA (fine needle aspiration test cytology): a small needle is used to collect a sample of the lump.
    • Biopsy: a bigger chunk of the lump is collected during surgery.
  • Request advanced imaging, such as CT scan, may be necessary in some cases.


Vet treatment

What are the treatment options for a cat with osteosarcoma?

There is no cure for osteosarcoma, and sadly, the majority of cats will not survive the disease.

However, treatment can improve your cat’s comfort and increase their survival time.

  • Treatment of choice for most cats is surgical removal of the primary tumour (may include amputation).
  • If there is evidence of metastasis, your vet may recommend chemotherapy after surgery.

Surgical removal of the tumour

Depending on the location, this will involve surgical removal of the affected bone.

When amputation is necessary, cats adapt incredibly well. Recovery is usually fast, within a few weeks.


May be recommended after surgery to help control the spread of the disease.

The protocol can vary. The procedure involves injecting a drug into the blood every couple of weeks.

Cats don’t have as many side effects from chemotherapy as humans. Occasionally, there is a temporary lack of appetite, nausea, tiredness and loose stools. These often last just a day or so after treatment.

Pain relief

Analgesic drugs: anti-inflammatories (NSAIDs), opioids, gabapentin, amantadine.

Bisphosphonates: their use can reduce bone pain and decrease bone destruction.

Radiation therapy: is another treatment option available. Although it’s not easily accessible and requires specific facilities and trained technicians.

Survival times

How long a cat will survive after diagnosis of bone cancer will depend on the location of the tumour as well as the extent of its spread.

Skull tumour location has lower survival rates compared to leg.

  • Without treatment: ~2 months
  • Only with palliative care (radiation and chemotherapy): ~3-6 months
  • Complete surgery removal but with metastasis: ~1 year
  • Complete surgery removal with no metastasis: ~2-4 years


Home treatment

Caring for your cat with osteosarcoma at home

If your cat has had an amputation, it’s important to highlight that they will gain good mobility soon after the amputation and live very comfortably.

Monitor your cat’s quality of life, any changes in behaviour, or any new signs that may indicate the spread of the disease.

When to consider euthanasia for a cat with osteosarcoma

After a diagnosis of bone cancer, and depending on the stage of the disease, your vet may offer euthanasia as a way to prevent suffering. When making this very emotional and hard decision, there are some tools that can help you find the right moment to say goodbye by looking for consistent deterioration and poor quality of life.

If you need help coping with grief and loss, you can contact us at Joii.



Can osteosarcoma in cats be prevented?

Sadly there is no known prevention for osteosarcoma.


When to worry

When to worry about your cat with osteosarcoma

Call your local vet if your cat shows any of these signs:

  • New limp or a limp that’s worsening
  • Collapsed or unable to rise
  • Lack of appetite, vomiting, or diarrhoea
  • Continues to lose weight
  • Pain
  • Deteriorating quality of life

Call Joii if:

  • You need help assessing pain in your cat
  • You need help assessing your cat’s quality of life
  • Your cat needs help adapting after amputation
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