How Quickly Can Feline Sarcoma Spread? The Need-To-Know Details


Sarcoma is an aggressive type of cancer that arises from connective tissues like fat, muscles, nerves, and blood vessels in cats. Sarcomas are locally invasive tumors that can metastasize to other parts of the body. There are several types of sarcomas that can affect cats, with fibrosarcomas being the most common. The goal of this article is to understand how fast sarcomas can grow in cats, as the growth rate has implications for treatment and prognosis.

Types of Feline Sarcoma

The main types of feline sarcoma include:

Fibrosarcoma – This is a cancerous growth presenting as a solid mass on the body or leg of a cat. Fibrosarcomas are the most common soft tissue sarcoma in cats [1].

Osteosarcoma – This type of sarcoma arises from bone cells and most often affects the legs of cats. Osteosarcomas can be very aggressive tumors [2].

Hemangiosarcoma – This is an aggressive, malignant tumor of blood vessel cells. Hemangiosarcomas often form as masses in the spleen, liver, or right atrium of the heart [2].

Histiocytic sarcoma – This rare tumor arises from histiocytes, a type of immune system cell. It can affect various parts of the body, including the spleen, liver, and intestinal tract [2].

Injection-site sarcoma – A tumor that develops at the site of a previous injection. These sarcomas are aggressive and require surgical removal [1].

What Causes Sarcoma

The exact causes of feline sarcomas are not fully understood. However, there are some factors that may increase a cat’s risk of developing sarcoma:

Inflammation: Previous inflammation or injury to a site can potentially trigger tumor formation. For example, cats vaccinated in the same location repeatedly over time may have inflammation that leads to sarcoma development at the injection site.[1]

Genetics: Purebred cats, especially Siamese and Abyssinians, seem to have a higher incidence of sarcomas. This suggests a possible genetic component.[2]

Environmental factors: Exposure to things like chemicals, radiation, or oncogenic viruses may play a role in sarcoma development in some cats.

Random DNA mutations: Like all cancers, DNA damage and uncontrolled cell mutations are ultimately what allows sarcomas to form and grow. The mutations leading to sarcoma likely arise randomly in most cases.

Overall, there is no one specific cause of feline sarcomas. Complex interactions between genetic, environmental, and random factors contribute to these tumors arising in cats.


Signs and Symptoms

As a feline sarcoma tumor starts to grow, owners may notice some subtle changes in their cat’s health and behavior. According to, the most common initial symptom is the appearance of a lump or mass somewhere on the body. These masses often start small but enlarge rapidly as the cancer progresses.

Cats may begin limping or adjusting their gait if the tumor is on a limb or located near a joint. They may seem hesitant to jump up on furniture or have difficulty using the litter box. Decreased appetite, vomiting, and weight loss can also occur as the cancer advances.

According to, some feline sarcomas are painfully invasive tumors that can erode into surrounding tissues and bone. Signs like yowling, aggression, or hiding could indicate the cat is experiencing significant discomfort.

Being attentive to changes in the cat’s health and notifying a vet promptly about any new lumps, limping, or concerning symptoms are key to early detection and more successful treatment.


To diagnose sarcoma in cats, veterinarians will first perform a thorough physical exam, inspecting and palpating the skin and other areas for abnormal growths or masses. They may notice signs like a lump or swelling beneath the skin that feels firm or solid. However, a biopsy is required for an official diagnosis of sarcoma.

There are different types of biopsies that may be performed. For example, a fine needle aspiration involves inserting a small needle into the mass to collect cells for examination under a microscope. A surgical, excisional biopsy removes the entire lump or a portion of tissue for biopsy.(1) This allows the vet to evaluate the size, margins, and invasiveness of the tumor.

Imaging tests like x-rays, CT scans, or MRI may also be used to determine the stage of the sarcoma by seeing how far it has spread. Chest x-rays can detect if cancer has metastasized to the lungs.(2) These tests along with the biopsy results provide key information for accurate diagnosis and staging of feline sarcoma.

Staging Sarcoma

Staging is the process of determining how extensive or advanced a sarcoma is at diagnosis. Staging is important because it helps determine the best treatment options and provides information about prognosis. There are four stages of sarcoma in cats:

Stage I – The primary tumor is small, less than 2 centimeters (cm), and has not spread to lymph nodes or other areas of the body.

Stage II – The primary tumor is larger, between 2-5 cm, but has not spread.

Stage III – The primary tumor is any size and may have spread to nearby lymph nodes, but not distant sites.

Stage IV – The cancer has spread (metastasized) to distant sites in the body such as the lungs, liver, or other organs.

To stage sarcoma in cats, vets will perform diagnostic tests like a physical exam, imaging tests (x-rays, ultrasound, CT or MRI scans), and possibly biopsies of lymph nodes to check for cancer spread. Imaging allows vets to see the size of the tumor and look for any potential metastases. [1]

Sarcoma Growth Rate

The growth rate of feline sarcomas can vary significantly depending on the type, grade, and location of the tumor. According to one 2022 study published in the National Library of Medicine, the median survival time for cats with grade I fibrosarcomas was 900 days. Grade II fibrosarcomas tend to be more aggressive, with a median survival time of 270 days in the same study.

Soft tissue sarcomas like fibrosarcomas often initially develop slowly and passively along tissue planes, according to the LIVS Feline Foundation. However, higher grade tumors have a greater likelihood of spreading to other parts of the body. Approximately 25% of high-grade soft tissue sarcomas will metastasize in cats.

Factors that impact growth rate and prognosis include the location of the tumor, how early it is diagnosed and treated, if the margins are clean after removal, and if chemotherapy is utilized after surgery. In general, sarcomas that are detected and treated early have a better prognosis.


There are several treatment options for feline sarcoma, including surgery, radiation therapy, and chemotherapy. Surgery is commonly used to remove the tumor. The goal is to completely remove the tumor with clean margins to help prevent recurrence. Even with clean margins, feline sarcomas tend to be locally aggressive and often regrow at the surgery site if microscopic disease is left behind[1]. For this reason, surgery may be combined with radiation therapy and/or chemotherapy.

Radiation helps kill remaining cancer cells after surgery. It can be used alone or with chemotherapy as an adjuvant therapy after tumor removal. Radiation therapy requires frequent visits over several weeks, but is an important part of treatment, especially for high grade sarcomas. Studies have shown that cats receiving surgery, chemotherapy, and radiation therapy have significantly longer tumor-free times compared to surgery alone[2].

Chemotherapy drugs may be injected directly into the tumor or administered systemically. The drugs kill rapidly dividing cancer cells. Chemotherapy is often used with surgery and/or radiation to help prevent recurrence and metastasis. The combination of treatments can improve prognosis and extend a cat’s life.

Managing Sarcoma

Sarcoma can be a challenging cancer to manage in cats, but there are some tips for providing the best care. According to the University of Florida Small Animal Hospital[1], the most important aspect is close monitoring after treatment. Your vet will want to examine the surgery site frequently to check for recurrence. Any new lumps or bumps should be evaluated right away.

Make sure your cat avoids licking or scratching the surgery site as it heals, as this can disturb the incision. Your vet may recommend an Elizabethan collar to prevent this. Providing soft bedding and litter can help reduce irritation as well.

It’s also crucial to carefully monitor your cat for signs of cancer recurrence, such as decreased appetite, lethargy, limping, or swelling around the surgery site. Catching a recurrence early maximizes treatment options. Routine bloodwork and imaging tests may be recommended to check for metastasis.

While sarcoma treatment focuses on surgery, chemotherapy or radiation therapy may sometimes be used. Work closely with your vet to manage any side effects from these treatments. Providing immune-boosting nutritional supplements can help support your cat during this time.

Most importantly, focus on maximizing your cat’s quality of life after sarcoma treatment. Cats with cancer need extra love and care. Make them as comfortable, stress-free, and happy as possible each day.


The prognosis for cats with sarcoma depends on several factors, including the type, grade, and stage of the tumor, as well as the treatment options pursued. According to one study, the median survival time for cats with grade I sarcomas was 900.5 days when treated surgically. Higher grade tumors are associated with more aggressive disease and shorter survival times. Surgical removal offers the best chance for a cure if the cancer has not spread. Chemotherapy and radiation may also be used after surgery to help prevent recurrence. Overall, early detection and treatment is key to improving prognosis.

Without any treatment, sarcomas in cats will continue to grow and spread to other parts of the body, significantly shortening life expectancy. In one study of untreated cats, median survival time was only 608 days. Cats with sarcoma should be evaluated by a veterinarian as soon as possible for staging and treatment recommendations. Catching the disease early on gives the best chance for long-term survival and quality of life.

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