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Fibrosarcomas In Cats

If you’ve ever seen your cat scurry up a tree or vault from the floor to a countertop, you know how agile they can be. Cats owe their athleticism, in part, to tendons, ligaments and cartilage, which connect muscles, bones and other internal body parts. Cancer that originates in these and other fibrous tissues are called soft tissue sarcomas, the most common of which is a fibrosarcoma. There are different types of fibrosarcomas in cats, ranging from an extremely rare, virus-associated form to subcutaneous tumors that are not uncommon. Depending on the type, a fibrosarcoma can metastasize (spread), including to the lungs and lymph nodes. While feline fibrosarcoma is treatable, it may not be curable in all instances. Catching fibrosarcoma early improves the chances for successful treatment, so pay attention to the potential signs outlined below.

Types of Fibrosarcomas In Cats

  • The most typical type of fibrosarcoma in cats manifests as tumors that can develop anywhere, from in the mouth and on the gums all the way back to a cat’s hind legs and even tail. A cat can also develop nasal fibrosarcoma, but it is rare.
  • Vaccine-associated fibrosarcomas can form at the site of a previous vaccination, such as a rabies shot. It is believed that these tumors are triggered by inflammatory responses to the vaccination. It could be six months or two to three years after the vaccination before this type of fibrosarcoma presents. It is important to note that vaccines help many, many cats — far more than the number that are at risk of cancer developing as the result of a vaccine.
  • A virus type of fibrosarcoma can strike cats as young as 1 or 2. It is extremely rare, however, with less than 1% of cats affected, and the cat must first be infected with the feline leukemia virus — otherwise, the fibrosarcoma virus cannot replicate. Notably, this type of fibrosarcoma is often resistant to treatment.
  • Trauma-related fibrosarcomas can form around a cat’s eye, sometimes several months or a year after the trauma occurred.

Symptoms of Fibrosarcoma In Cats

Fibrosarcoma in cats is marked by a variety of symptoms. They can differ depending on where the tumor is, the size and to which stage the cancer has progressed.

  • Oral fibrosarcoma in cats typically presents as a mass in the mouth, sometimes with a “cauliflower”-like, bumpy appearance on the gums. A stricken cat also may experience oral bleeding or have trouble eating due to discomfort or the size of the mass. He or she might drool if the mass is sizable. Bad breath is another potential symptom. Cat parents may not typically check their pet’s mouth, but it can be helpful to do so in order to be able to spot fibrosarcoma symptoms early.
  • A fibrosarcoma in a cat’s nasal passages can disrupt his or her breathing, causing sneezing or snorting and making him or her sound congested. Nasal discharge, which may be bloody, is another potential symptom.
  • Fibrosarcomas most often appear as bumps or lumps anywhere else on the outside of a cat’s body. Some tumors grow subcutaneously (beneath the skin), resulting in a bulge. They can develop on the head and neck, the trunk, the limbs and even between a cat’s toes. With the virus-type of fibrosarcoma, the tumors tend to be all over the body, appearing like marbles under the cat’s skin. Petting your cat regularly with the specific intent of feeling for bumps can help you detect fibrosarcoma early.
  • Lastly, though uncommon, cats can develop a fibrosarcoma on the internal organs such as the spleen.
Cat getting a checkup

Diagnosing Fibrosarcoma in Cats

Some symptoms of fibrosarcoma in cats are also symptoms of other diseases or conditions. So, if your cat has a growth that you are concerned about or is showing any other symptoms, you should see a veterinarian to get an accurate diagnosis. You can also learn about the various stages of feline fibrosarcoma and the best ways to treat your cat based on his or her specific circumstances.

A diagnostic visit typically involves full bloodwork, including a complete blood count (CBC) and chemistry profile, accompanied by a urinalysis. If possible, your veterinarian also will take a tissue sample to send to a lab for analysis. Depending on where the tumor is and other factors, collecting the sample is done via a fine needle aspiration or biopsy/excision. A CAT scan may be ordered to help determine the extent of the disease, especially if the suspected cancer is in an area such as the nasal passages, where a tumor also can infiltrate into the sinuses. It can be difficult to get a tissue sample from this area. Thus, a rhinoscopy or an incisional biopsy also may be ordered. Additionally, a stricken cat should undergo three-view chest X-rays to rule out the possibility of metastasis (spread) to the lungs.

Feline Fibrosarcoma Treatment and Prognosis

Surgery and/or radiation are often the mainstay of treatment for feline fibrosarcoma. The combination indicated will depend on your cat’s unique circumstances. Treatment may be curative or it may put the cancer in a remission for a period of time, so as to improve your cat’s quality of life and extend your time together. Even with treatment, there is also the possibility that the cancer will return at some point.

Treatment for Oral Fibrosarcoma

For a cat with an oral tumor, treatment is often aggressive. Options include debulking surgery to remove as much of the fibrosarcoma tumor as possible without damaging other tissues in the area. With just this option, tumors often recur quickly. A more aggressive option is definitive surgery which involves the removal of a portion of the cat’s jawbone to remove the main bulk of the mass and to attempt to obtain wide margins. (“Wide margins” means the outer edges of the removed tissue are not cancerous, which indicates that all the cancer has been removed.)

Notably, oral fibrosarcoma tends to return, and it could be a matter of weeks or months. Due to this possibility, surgery is often followed by radiation. There are two primary types of radiation — conventionally fractionated radiation therapy (CFRT) and stereotactic radiation (SRS). SRS is more innovative, as higher doses of radiation and precision targeting are used to try to eliminate, shrink or control the tumor. SRS requires fewer treatments (1 to 3, vs. 15 to 21 with CFRT), which has the added benefit of reducing the number of times a cat must be anesthetized. SRS also can be the primary treatment option if surgery is ruled out for any reason. Successful radiation improves the cat’s quality of life and can extend your time together for six to 12 months.

If all treatment options are declined, an oral fibrosarcoma will continue to grow. A cat will eventually have difficulty eating, and his or her quality of life will decline, leaving a pet parent to face a decision about euthanasia.

Treatment for Nasal Fibrosarcoma

Removing a fibrosarcoma from inside the nose is rarely advised and often provides little benefit. It’s impossible to achieve the goal of clean margins. Radiation is the treatment of choice, with the SRS option again providing the benefits of fewer treatments and anesthetic events compared to CFRT. Treatment often can extend a cat’s life by six to 12 months. One potential side effect is postnasal drip as cancer cells die and exit the nasal passages.

Treatment for Fibrosarcoma Tumors on or Under the Skin

Surgery and/or radiation are typically the recommended treatments for fibrosarcomas on or under a cat’s skin. Early treatment is obviously best and important because there is a 10-25% percent chance of the cancer spreading to lymph nodes or the lungs, depending on how the tumor is graded (Grade 1, 2 or 3). With surgery, the goal is to achieve wide margins — at least 3 centimeters around the mass. In the absence of that, it’s not unusual for cancer to return in a period of weeks to months. When surgery is followed with radiation, some cases can maintain a long remission of years

If a fibrosarcoma is on the distal part of a tail or the distal part of a limb, amputation of that tail or limb can yield wide enough margins so that the feline is cured.

Stereotactic radiation also can be effective as a standalone treatment if surgery is ruled out for any reason. Sometimes SRS is also used before surgery to reduce the size of a tumor if it’s otherwise too large to remove.

In the absence of any treatment, a fibrosarcoma tumor will continue to grow. Grade 1 and Grade 2 tumors can grow very, very slowly. Although such masses may not be painful, they can eventually grow quite large and become cumbersome for a cat.

Chemotherapy for Fibrosarcoma

Chemotherapy is not typically the first treatment choice for feline fibrosarcoma but it might help slow subcutaneous tumors for those cases with highly aggressive disease (grade 3) or if the pet family wants to try some therapy yet declines surgery and radiation therapy. Typically, chemotherapy pills are given on an every-other-day basis. Chemo also would necessitate periodic visits to your veterinary medical oncologist to assess efficacy and to perform bloodwork to ensure that treatment is not affecting the body’s functions. If your cat has aggressive, Grade 3 fibrosarcoma, an oncologist may recommend a combination of radiation and chemotherapy. It’s important to note that there is the possibility that chemotherapy will be of little aid help fighting this disease.

Treatment for Vaccine-Associated Fibrosarcoma

Surgery and/or radiation are still the top treatment choices for a cat with virus-associated fibrosarcoma, but there are post-treatment differences. Because the fibrosarcoma stemmed from a vaccine reaction, expect your cat’s medical team to recommend that future vaccines not be given between the shoulder blades or the trunk of the body. Essential vaccines can still be given in the distal part of a leg or the tail as those can be amputated if a reaction leads to a fibrosarcoma developing. This type of fibrosarcoma in cats often cannot be cured without amputation.

Treatment for Splenic Fibrosarcomas

A splenectomy, or surgical removal of the entire spleen, is often the treatment of choice for these tumors. Adult cats typically do quite well despite not having a spleen.

PetCure Oncology and Feline Fibrosarcoma Treatment

PetCure Oncology specializes in treating cancer in cats, including fibrosarcoma. We offer an array of modern treatment options and are a pioneer in the industry when it comes to advanced stereotactic radiation. We’re not just about science-backed medical treatment — our compassionate side drives our mission, which is providing your cat the best quality of life possible while extending your time together. For more information about cancer treatments for your cat, find a location near you and contact us today.

The contents of this article were provided in part by Dr. Renee Alsarraf, DVM, DACVIM (Oncology), a board-certified veterinary medical oncologist and member of PetCure Radiation Oncology Specialists (PROS).

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