A watercolor painting of a woman holding a cat.

What is Osteosarcoma in Cats?

What is it?

Osteosarcoma is a type of bone cancer that affects cats. It often affects the legs or jawbone. It can be aggressive cancer that spreads quickly to other body parts.

How is it Treated?

Treatment for osteosarcoma in dogs usually involves a combination of chemotherapy and surgery. First, the affected limb may need to be amputated, followed by chemotherapy to kill any remaining cancer cells. Additional treatments, such as radiation therapy or immunotherapy, may also be recommended depending on the severity and stage of cancer.

Breed Predispositions

Siamese and Burmese cats.


Jessie, a dedicated cat owner, always looked forward to her evenings spent cuddling with her beloved feline, Whiskers. However, she recently noticed that Whiskers was limping and appeared to be in pain. Concerned, Jessie took Whiskers to their trusted veterinarian for a thorough examination. The vet ran several tests and discovered that Whiskers had osteosarcoma, a type of bone cancer. Shocked and heartbroken by this news, Jessie knew she had to learn everything she could about this disease to provide Whiskers with the best care possible.

Osteosarcoma in cats is a type of cat cancer primarily identified as a malignant bone tumor. It stems from the cells that contribute to the formation of bones. Certain processes within the feline body can trigger these abnormal bone cells’ uncontrolled growth and multiplication. This primary bone tumor can impact various bones within the cat’s body, but it’s frequently found in the long bones, such as those in the limbs, in appendicular osteosarcoma.

The tumor can invade nearby tissues and metastasize to different body parts. Understanding what osteosarcoma is considered in cats aid in the timely recognition of the condition and providing appropriate veterinary care without delay.

Types of Bone Tumors in Cats

Osteosarcoma in cats is often classified based on location, appearance under the microscope, or degree of malignancy.

Based on Location:

  1. Appendicular Osteosarcoma: This type of osteosarcoma occurs in the long bones of the limbs, such as the femur, tibia, humerus, and radius. In cats, appendicular osteosarcoma is less common than in dogs.
  2. Axial Osteosarcoma: Axial osteosarcomas develop in the bones of the skull, spine, ribs, or pelvis. This type is more common in cats.

Based on Microscopic Appearance:

  1. Osteoblastic Osteosarcoma: This is the most common type of osteosarcoma. Under a microscope, these tumors show cells that resemble osteoblasts (the cells that produce new bone) and produce an osteoid (bone-like) matrix.
  2. Chondroblastic Osteosarcoma: These tumors have areas that resemble cartilage under the microscope.
  3. Fibroblastic Osteosarcoma: These tumors have areas that resemble fibrous tissue under the microscope.

Based on the Degree of Malignancy:

  1. High-grade Osteosarcoma: These are the most aggressive type of osteosarcoma and are likely to spread to other body parts (metastasize).
  2. Low-grade Osteosarcoma: These osteosarcomas are less aggressive and less likely to metastasize. They still, however, need to be treated as they can cause local bone destruction and pain.

Regardless of the type, osteosarcoma is a serious and potentially life-threatening condition that requires immediate veterinary attention.

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The prognosis for cats with osteosarcoma varies greatly depending on the type, location, stage of the disease at diagnosis, and the treatment given.

Causes of Osteosarcoma in Cats

Osteosarcoma is an aggressive form of feline cancer that manifests within the bone structure. It’s a potent disease that can spread, with up to 90% of osteosarcoma instances metastasizing to a cat’s lungs. Although it’s commonly found in dogs, cats aren’t exempt from the disease. The exact origins of how osteosarcoma develops in cats remain a mystery. Still, several factors are believed to amplify a cat’s risk of acquiring this disease, considered a rare cancer in cats.

Here are some potential influencing factors:


Cats advanced in years, particularly those over 10, tend to be more susceptible to osteosarcoma than their younger counterparts. The explanation behind this trend isn’t fully comprehended. Still, it’s widely accepted that the likelihood of contracting various forms of cancer elevates with age due to the accumulation of genetic mutations and the degeneration of the immune system.


Certain breeds of cats, such as Siamese cats, are noted to have a higher susceptibility to osteosarcoma, implying a potential genetic predisposition. Breed-specific preferences for various types of cancer usually trace back to certain genetic traits more prevalent in those breeds.

Prior Bone Injury or Surgery

Some theories propose a connection between primary bone lesions or surgical procedures and the onset of osteosarcoma, sometimes called “osteosarcoma of the bone scar.” The hypothesis suggests that injuries or surgeries may trigger the cells in the bone to divide and mend the damage. This escalated cellular activity could theoretically pave the way for cancer development. However, this theory requires further validation through more intensive research.

Carcinogen Exposure

In several animals and humans, exposure to specific carcinogens such as radiation has been linked with a heightened risk of osteosarcoma. For instance, in human cases, a history of radiation therapy can elevate the risk of osteosarcoma developing within the irradiated area. Similar studies in cats are needed.


While the precise genetic modifications causing osteosarcoma are yet to be identified, it’s believed that alterations in several genes might be at the helm of this cancer’s development. The associated genetic changes could be inherent or acquired during the cat’s lifespan due to exposure to environmental factors or random events during standard cell division.

It’s important to remember that the presence of one or multiple risk factors does not inevitably lead to osteosarcoma. Many cats with these risk factors never manifest the disease, whereas some without known risk factors do. Investigations into the causes of this aggressive cancer in cats are ongoing, and our comprehension of this complex disease continues to evolve. If you harbor concerns about your cat’s susceptibility to developing osteosarcoma, it’s advisable to consult with your veterinarian.

Symptoms of Osteosarcoma in Cats

Osteosarcoma, a variant of bone cancer, can manifest various symptoms in feline patients, largely dictated by the tumor’s location. Here’s a list of potential indications:

  • Lameness or Limping: Among the more prevalent symptoms is limping or lameness, especially when the affected bone is within a limb. Initially, this might emerge as an erratic issue, gradually escalating to persistent lameness as the disease progresses. fsdfj
  • Bone Pain: Osteosarcoma is notorious for causing significant bone pain. Indicators of your cat’s discomfort might include restlessness, reduced activity, decreased appetite, or vocal expressions of pain.
  • Swelling: Swelling in the vicinity of the tumor might become noticeable. This symptom is particularly observable if the tumor is situated on a limb or close to the body’s surface.
  • Fractures: As osteosarcoma undermines the bone’s structural integrity, it could lead to pathologic fractures. Such fractures result from minimal trauma, owing to the weakened condition of the bone.
  • Weight Loss: Mirroring many types of cancer, cats grappling with osteosarcoma might exhibit weight loss, commonly triggered by diminished appetite or the body’s reaction to cancer’s presence.
  • Lethargy or Decreased Activity: Cats battling osteosarcoma might display lowered energy levels and opt to spend more time in sleep or rest. They might also exhibit reluctance to undertake activities like jumping or climbing.
  • Respiratory Distress: If the osteosarcoma has metastasized or spread to the lungs, your cat might exhibit signs of respiratory distress such as coughing, labored breathing, or rapid breaths.

Notably, these symptoms might also suggest other health conditions and are not exclusive to osteosarcoma. Should you observe any behavioral changes, shifts in appetite, or overall health alterations in your cat, prompt veterinary consultation is crucial. A timely diagnosis and treatment can substantially bolster the prognosis for numerous health conditions, osteosarcoma included.

Diagnosis of Bone Cancer in Cats

Diagnosing osteosarcoma in felines encompasses a mix of physical examination, historical analysis, and a range of diagnostic assessments. Here’s an outline of the process:

Initial Evaluation and Physical Examination

The veterinary professional will start with inquiries about your cat’s overall health, changes in behavior, or evidence of discomfort, such as limping or mobility difficulties. Queries will also be made regarding the timeline and progression of these symptoms. The physical examination involves a thorough evaluation of your cat’s body. If a lump or bone deformation is suspected – a potential sign of appendicular OSA or a nasal tumor – the vet will palpate the area to determine its size, location, firmness, and potential to cause pain. This stage is vital in dictating subsequent diagnostic steps.

osteosarcoma in cats

Radiographic Examination (X-Rays)

X-ray imaging, including thoracic radiographs and chest X-rays, typically represents the initial diagnostic test undertaken when suspected of osteosarcoma. X-rays can reveal the tell-tale signs of osteosarcoma, inclusive of a ‘moth-eaten’ appearance where the bone is undergoing degradation, new bone growth areas, and signs like an aggressive bone pattern or a ‘sunburst’ pattern suggesting the tumor is invading surrounding tissues. Chest X-rays may also be used to inspect for metastasis signs, as the lungs are a primary tumor metastasis site in osteosarcoma cases.

Blood Analysis

This incorporates a complete blood count (CBC), which screens for anemia symptoms (reduced red blood cell count) or infection (elevated white blood cell count). A biochemical profile that evaluates kidney, liver, and pancreatic function, alongside sugar and protein levels, is also included. These assessments can yield crucial data about your cat’s overall health and capacity to tolerate the anesthesia frequently required for additional diagnostic procedures or treatments.

Bone Biopsy

A biopsy involving a sample from the affected tissue (bone biopsy) is the gold standard for diagnosing osteosarcoma. There are primarily two types of biopsies.

  • A fine needle aspiration inserts a slender needle into the tumor to extract cells. This procedure often circumvents the need for anesthesia. However, it may not always provide a definitive diagnosis as it might necessitate collecting more cells or specific cell types.
  • A surgical biopsy that retrieves a larger tissue sample is performed under general anesthesia. Although more invasive, it presents a larger sample for the pathologist to study, which enhances the likelihood of a definitive diagnosis.

Advanced Imaging

Sophisticated imaging methodologies like computed tomography (CT scan) or magnetic resonance imaging (MRI) furnish images with greater detail than conventional X-rays. These prove highly useful in assessing the extent of the tumor, its relationship to nearby structures, and in surgery planning, if necessary.

Cancer Staging

Staging is a mechanism to discern the extent of cancer spread within the body. It usually involves additional X-rays or abdominal ultrasounds to check for internal organ spread. A CT scan can provide a more detailed chest and abdomen view, useful in instances where metastasis is suspected but not confirmed through X-rays. Occasionally, a regional lymph node, lung, or other organ biopsy may be necessary if metastasis is suspected.

The outcomes of these tests, in conjunction with the cat’s overall health and age, assist the vet in formulating the most suitable treatment plan and prognosis.

Remembering this process can vary depending on the case specifics and the vet’s preferences is important. Always communicate with your vet if you have concerns about the diagnosis process and available treatment options.

Treatment Options for Feline Osteosarcoma

Interventions for osteosarcoma in felines can encompass an array of modalities, such as surgery, chemotherapy, and palliative care, hinging on the disease’s progression and the cat’s overall well-being. Let’s examine some alternatives:

Surgical Intervention

Surgical intervention is the primary treatment route for localized osteosarcoma or axial osa. The objective is to excise the tumor and a margin of healthy tissue surrounding it to ensure no cancer cells linger. Often, this involves limb amputation alone for skeletal tumors present in the limbs. While the prospect of amputation can be emotionally challenging for many pet owners, it’s crucial to recall that cats generally adapt well to a three-legged life, and it can provide substantial pain relief.

For osteosarcoma tumors not located in the limbs or those unsuitable for amputation due to size or location, alternative surgical options, like limb-sparing surgery or partial bone removal, might be considered, though they are less frequently executed as an alternative to amputation.

Chemotherapeutic Treatment

Post-surgery, chemotherapy might be suggested to eradicate any remaining cancer cells and lower the risk of cancer metastasizing to other body parts. Cats usually tolerate chemotherapy well, and it does not typically induce the same side effects as observed in humans. However, possible side effects can comprise nausea, loss of appetite, and a reduced white blood cell count, rendering the cat more vulnerable to infections.

Radiation Therapy

Radiation therapy might be employed as a standalone treatment or in combination with surgery and chemotherapy in certain cases. Radiation therapy utilizes high-energy rays to annihilate cancer cells and shrink tumors. It is generally employed for tumors that are not completely removable via surgery or palliative care to alleviate pain and enhance the quality of life.

Management of Pain and Palliative Care

Whether curative treatment is pursued or not, pain management for the cat is vital. This could include medications like nonsteroidal anti-inflammatory drugs (NSAIDs), opioids, and other analgesics. Palliative radiation therapy might also be employed to help control pain. Moreover, some cats may benefit from complementary therapies like acupuncture or physical therapy.

Participation in Clinical Trials

New interventions for osteosarcoma are under constant research and development, and occasionally, clinical trials are available which may offer access to these cutting-edge treatments.

The optimal treatment approach for each cat hinges on various elements, including the tumor’s location and stage, the cat’s overall health, and the owner’s preferences. Treatment seeks to control cancer, alleviate pain, and preserve the cat’s best possible quality of life. Engaging in a comprehensive discussion with the veterinarian or a veterinary oncologist is vital to understand the treatment options available and their implications for the cat’s prognosis and quality of life.

Prevention of Feline Bone Cancer

The precise origins of osteosarcoma in cats remain undefined, making it challenging to outline specific preventative measures. Nevertheless, there are some fundamental steps that cat owners can implement to help uphold their cat’s overall health and potentially lessen the chance of developing various forms of cancers.

Nutritionally Balanced Meals

Providing your cat with a balanced, nutritionally complete meal plan is essential for overall health and disease prevention. A health-conscious diet can contribute to sustaining a robust immune system, which can help the body ward off diseases.

Frequent Physical Activity

Consistent physical activity assists in maintaining healthy bones and joints while promoting general health. Cats should be incentivized to partake in play and exercise routinely to help maintain a healthy weight and body condition, thus extending the median survival time even following amputation in case of osteosarcoma.

Routine Veterinary Check-ups

Scheduled vet check-ups are crucial for identifying health problems, including cancer. Most forms of cancer, including osteosarcoma, are more effectively treated when identified early. Your vet can conduct physical exams and diagnostic tests to monitor your cat’s health and detect potential health issues.

Limit Contact with Carcinogens

While the link between exposure to environmental carcinogens and the development of osteosarcoma in cats has not been extensively studied, it’s generally advisable to limit your cat’s exposure to known carcinogens such as tobacco smoke.

Genetic Considerations

Certain breeds and larger cats might have an elevated risk of developing osteosarcoma, implying a potential genetic element. Although you can’t alter your cat’s genetics, being aware of this risk can facilitate early detection and intervention.

It’s essential to remember that despite the best preventive care, averting cancer is not always feasible. However, these measures can contribute to enhancing your cat’s overall health and quality of life, and early detection and treatment can often lead to improved outcomes.

Frequently Asked Questions

Detecting osteosarcoma in cats typically involves observing clinical signs and symptoms such as lameness, swelling or a firm mass at the site of the tumor, pain or discomfort, and changes in behavior or activity levels. However, these signs can be nonspecific and may be seen with other conditions. A definitive diagnosis of osteosarcoma is made through imaging techniques like X-rays, ultrasound, or CT scans and confirmed by obtaining a tumor biopsy for histopathological examination.

The prognosis for cats with osteosarcoma depends on various factors, including the location and extent of the tumor, the presence of metastasis (spread to other areas), the grade of the tumor, and overall health and age. Osteosarcoma in cats is generally aggressive and has a guarded prognosis, but the specific outlook can vary. Treatment options like surgery, chemotherapy, or radiation therapy can help improve the prognosis and extend survival time. However, the prognosis remains generally less favorable compared to some other types of cancer in cats.

Osteosarcoma is primarily a disease seen in cats and dogs, but it is very rare for it to be transmitted from one animal to another. Osteosarcoma is not considered a contagious disease, and the risk of spreading the condition from an affected cat to other animals is extremely low.

The survival time for cats with osteosarcoma can vary widely depending on several factors, including the extent of the disease, the response to treatment, and the cat’s overall health. Unfortunately, osteosarcoma is typically aggressive cancer with a guarded prognosis in cats. On average, cats with osteosarcoma may survive for several months to a year with appropriate treatment. However, it is important to consult with a veterinarian who can provide a more accurate prognosis based on the specific circumstances of the cat’s condition.

Common warning signs of osteosarcoma in cats include lameness, swelling or a firm mass at the tumor site, pain or discomfort, limping, decreased mobility or reluctance to move, and changes in appetite or behavior. It is important to note that these signs can also indicate other conditions. Hence, a thorough evaluation by a veterinarian, including imaging and biopsy, is necessary to confirm the diagnosis.

If osteosarcoma is left untreated, the tumor can continue to grow and invade surrounding tissues, leading to increased pain, loss of function, and potential complications such as fractures or infections. Osteosarcoma is aggressive cancer; without intervention, the disease will progress, potentially leading to a decreased quality of life and shortened survival time for the cat.

The behavior of cats with a tumor can vary depending on factors such as the location and size of the tumor, the presence of pain or discomfort, and the cat’s overall health. Some cats may show signs of pain or discomfort, such as vocalizing, restlessness, or aggression when touching the tumor. Cats may also exhibit changes in appetite, weight loss, lethargy, or altered behavior. However, it is important to note that these signs can be nonspecific and may also be seen with other medical conditions. Hence, a thorough veterinary evaluation is necessary to determine the underlying cause.

Certain factors may increase the risk of cats developing bone cancer, including age (older cats are more commonly affected), breed predispositions (e.g., Siamese cats are more susceptible to osteosarcoma), and previous history of bone tumors. However, cat bone cancer is still relatively rare, and the exact cause and risk factors are not fully understood.

Diagnosing primary bone tumors in cats typically involves a combination of physical examination, imaging techniques (X-rays, CT scans), and histopathological examination of a biopsy. X-rays can help identify abnormalities in the bone structure, such as bone destruction or new bone formation. CT scans provide more detailed imaging and can help evaluate the tumor’s extent and metastasis’s presence. A biopsy, which involves obtaining a tumor tissue sample, is necessary to confirm the diagnosis and determine the specific type and grade of the tumor.

Bone cancer, including osteosarcoma, can be painful for cats. The growth of the tumor within the bone can cause bone destruction, inflammation, and nerve compression, leading to discomfort and pain. Cats may exhibit signs of lameness, reluctance to move, vocalization when the affected area is touched, or changes in behavior due to the pain associated with bone cancer. Pain management is essential to the treatment plan for cats with bone cancer to ensure their comfort and well-being.

The prognosis for cats with osteosarcoma is generally guarded due to the disease’s aggressive nature. The specific prognosis can vary depending on the tumor’s location and extent, metastasis’s presence, the response to treatment, and the cat’s overall health. With appropriate treatment, including surgery, chemotherapy, or radiation therapy, survival times can range from several months to over a year. However, it is important to consult with a veterinarian who can assess the individual case and provide a more accurate prognosis based on the specific circumstances of the cat’s condition.

Disclaimer: The information provided on this veterinary website is intended for general educational purposes only and should not be considered as a substitute for professional veterinary advice, diagnosis, or treatment. Always consult a licensed veterinarian for any concerns or questions regarding the health and well-being of your pet. This website does not claim to cover every possible situation or provide exhaustive knowledge on the subjects presented. The owners and contributors of this website are not responsible for any harm or loss that may result from the use or misuse of the information provided herein.

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