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Bone Cancer in Cats: Symptoms, Diagnosis, and Treatment

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Bone Cancer in Cats: Symptoms, Diagnosis, and Treatment

Posted by Julianne Macaraeg on
Updated at: January 07, 2021

Common Types of Cat Bone Cancer 

Osteosarcoma: Bone Cancer in Cats

Also known as osteosarcoma, bone cancer is a common diagnosis in felines. Tumors, unfortunately, come in a variety of sizes, and the placement of a cancerous tumor in cats can be almost anywhere. Adding to the wide variation of bone cancer, there are also two different types of bone tumors. 

As you will learn from the vet, your cat will have either a primary tumor or a secondary tumor. A primary tumor is a mass of cancerous cells that form in the bone themselves, whereas a secondary tumor grows somewhere near or around the bone instead of in the bone directly. Usually, secondary tumors will arise in bone marrow. 

Even though bone cancer is a serious matter, it is not as dangerous as other types of feline cancers, like cell carcinoma. A cell carcinoma tumor forms in the skin of our feline friends, and it creates far more causes for concern than feline bone cancer. Let's take a closer look at the primary tumors because there are actually four different types of primary tumors in cats! 

The Four Kinds of Primary Tumors that Cats Can Develop

As mentioned, within the category of primary tumors in cat bones, there are four different kinds of tumors. All of these tumors grow in the bones of cats, but what sets them apart is the part of the bone that they originate from. 

These four types of primary bone tumors in cats are… 

  • Chondrosarcoma 
  • Fibrosarcoma 
  • Hemangiosarcoma 
  • Osteosarcoma 

Dogs are far more likely to develop primary bone tumors than cats, though it is still possible for cats to have primary tumors despite being very unlikely. When they do grow from the bones of cats, these primary tumors are not aggressive in most cases. 

Feline bone tumors tend to be more benign than anything, which is good news for cats. Of the four primary bone tumors in cats, the most frequently diagnosed tumor is osteosarcoma. The other three types of primary tumors are not as common in cats. Let’s take a look at these four primary tumors more closely! 


Like other types of primary tumors, chondrosarcoma is very rare in cats. Our feline friends are not at a high risk for chondrosarcoma, though it might still develop in unusual circumstances. This type of sarcoma grows from cartilage, so it's likely you'll find a primary chondrosarcoma tumor in the connective cartilage between a bone and a joint. 


Fibrosarcoma is one of the more common types of bone cancer. It takes a lot for fibrosarcoma cells to metastasize and spread via the lymph nodes to other parts of a cat's body, but even so, the fibrosarcoma cells are very aggressive at their site of origin. This is what professionals refer to as a locally aggressive type of cancer. 

The exact cause of fibrosarcoma is still up in the air because researchers believe there could be multiple contributing factors of feline fibrosarcoma. However, a commonality among cats that are diagnosed with fibrosarcoma tumors is vaccination. 

It's not as though a specific vaccine is causing fibrosarcoma in cats. Instead, the tumors tend to originate at the site where the needle was injected into the cat's skin. In other words, fibrosarcoma is categorized as a vaccine-associated sarcoma, or VAS for short. 


Hemangiosarcoma is a type of bone cancer that arises from blood vessels. Despite being very uncommon, the tumors are quite aggressive when they metastasize. Not only does hemangiosarcoma pose a major threat as it begins to spread throughout the body, but veterinarians are not sure what causes hemangiosarcoma to grow in the first place. 

Hemangiosarcoma cells are not limited to the bones either. Once they begin metastasizing, these cells can permeate all throughout the body and impact just about every internal organ possible, which leads to a very low survival rate amongst cats that develop hemangiosarcoma. 


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Osteosarcoma is one of the most uncomfortable types of cancer in cats. It creates a lot of physical discomfort for cats with osteosarcoma tumors, which also means that these tumors are more noticeable than many other tumors in cats. 

The main reason for this serious discomfort is that osteosarcoma creates a malignant tumor, meaning it is very dangerous and often fatal. The cells that osteosarcoma develops from are called osteoclasts and osteoblasts. These two cell types are essential for bone health, so the fact that cancer grows from these cells is scary. 

It disrupts the natural growth and production of bone cells, which ultimately weakens your cat's bones. They start to lose strength quite rapidly and it leads to physical discomfort in the affected limb.  Professionals are not sure what exactly causes osteosarcoma in cats. 

Are Primary Bone Tumors Common in Cats? 

Usually, cats will develop secondary bone tumors. Primary tumors are rare in cats. Of the four types of primary cancerous tumors in cats, osteosarcomas are the most common. 

What Are the Symptoms of Feline Bone Cancer? 

The exact symptoms that your cat experiences will depend on your cat’s specific situation. Each type of tumor can yield different side effects, so you might notice your cat acting in ways that are not listed here. 

If you see anything concerning and you are worried about your cat’s behavior, please contact your pet’s veterinarian. It’s best to have your cat checked out as soon as you start to feel that something is wrong. Even though some symptoms might be different depending on the type of tumor, there are many similar symptoms that cats with bone cancer experience. 

In general, the clinical signs of bone cancer in cats include… 

Symptoms of Bone Cancer in Cats | Innovet Pet
  • Visible mass or lump
  • Loss of appetite 
  • Weight loss
  • Swollen lymph nodes
  • Hard time chewing 
  • Difficulty eating in general 
  • Seizures or dizziness 
  • Fainting spells 
  • Problems with breathing 
  • Sensitivity to being pet 
  • No interest in playing
  • Unable to walk for long periods 

How is Bone Cancer Diagnosed in Cats? 

There are a few different ways of diagnosing bone cancer in cats. 

Blood tests are one of many types of diagnostic tests for cats showing signs of cancer. Blood tests can give insight into your cat's ALKP levels. Short for alkaline phosphatase, ALKP is a sign of damage caused by tumors in cats. Blood tests are also helpful when looking to rule out certain types of cancer in feline bones, like hemangiosarcoma cells. 

Another common way of diagnosing feline cancer is by conducting a bone biopsy. This diagnostic option usually follows other attempts to diagnose the issue, like the blood exams we mentioned. Essentially, during a biopsy, the vet will utilize local anesthesia to keep your cat calm during the procedure. 

The vet will withdraw a sample of cells from the tumor using a needle to extract them from the body. The medical professionals will examine the sample they took from the suspicious mass and determine whether or not the cells are cancerous. From there, they will let you know which steps you should take next. 

How to Treat Bone Cancer 

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There are a few treatment options for cats with tumors of the bone. There are two goals in mind when treating cancer of feline bones. First, it's important to make sure your cat is comfortable, so the vet will want to treat any pain that your cat is experiencing. 

Usually, this involves pain control methods that manage the discomfort and make the situation less grueling for your cat. Examples of pain management treatment options are medication, radiation therapy, and possibly surgical removal of the tumor, if worse comes to worst. 

This further prevents the tumor from getting better and the cancerous cells from metastasizing to other parts of your cat's body. Tumors that remain local are a lot easier to get rid of than tumors that start spreading elsewhere, so radiation helps with keeping tumors localized. Radiation is frequently used in tandem with chemotherapy for treating cancer. 

Other treatment options include… 

  • Amputation 
  • Chemotherapy 
  • Partial surgical removal 

The side effects of these three options can be very hard on your cat, so usually, these are saved as a last resort. However, the exact treatment plan that your vet advises you to follow will fully depend on your cat’s situation. Please be sure to follow your vet’s instructions in order to avoid any adverse side effects. 

The right combination of treatment options will ensure that your cat is as comfortable as possible while living with cancer of the bones. If you have any questions or concerns regarding your cat’s cancer treatment, consult the vet immediately. They are there to help you understand what is going on and they are striving to ensure that your feline friend gets healthy again.


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