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Fibrosarcoma in Cats: Symptoms, Diagnosis & Treatment

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Fibrosarcoma in Cats: Symptoms, Diagnosis & Treatment

The term fibrosarcoma before might be unfamiliar, but it's used to refer to skin tumors or tumors that develop on the soft tissue.

The official name refers to these tumors growing from fibroblasts (connective tissue cells), but they don't form there exclusively. Feline fibroblast sarcoma also arises in the subcutaneous connective soft tissue.

This article wants to introduce you to this disease and let you know how vaccine-associated sarcomas in your cat are diagnosed and treated.

Possible Causes of Cat Fibrosarcoma

With cat tumors, it can be challenging to pinpoint the root cause. At its core, this type of skin cancer tumor arises when cancerous cells begin to grow rapidly and eventually outnumber the healthy cells. 

So, what causes the initial growth in the first place? The answer to this question depends on the type of skin cancer tumors involved.

There are two major root causes. Firstly, it is a vaccine-associated sarcoma meaning it can appear after a vaccine. Secondly, fibrosarcomas can also arise from a virus.

Vaccine-associated sarcoma

A local vaccine-associated sarcoma is one that grows at the place where the feline receives a vaccination. The majority of vaccination sites usually heal, and the small tumor goes away in due time, but on rare occasions, the mass grows. This mass develops in the soft tissues on or around the vaccination/injection site. Since felines most often receive vaccines between their shoulder blades or in their lower back, it is common for tumors on cats to arise there.  

What Are the Symptoms of a Fibrosarcoma Cat?

A vaccination is a primary cause of these benign and malignant local cases. Cats can develop symptoms as a side effect of a vaccination, which then develops into more concerning symptoms signaling that something isn't right.

Fibrosarcoma is often caused by a tumor that forms at the injection site of a vaccine. A potential sign is that the tumor does not resolve itself and instead grows. As it grows, it means the cancerous cells are multiplying, meaning the tumor is malignant.

When a malignant tumor gets bigger, the likelihood that the cancerous particles will spread increases. Once they spread to other parts of the body, more symptoms will appear. 

A weakened immune system and weight loss in your felines are other symptoms of this disease.

It is important to note that things like weight loss could also be symptomatic of other issues. If you see it in your pet, take them to a veterinarian to get a proper diagnosis.

How To Get a Diagnosis 

There are many ways of diagnosing the disease. A few examples of the most common diagnostic tests include. 

  • Needle aspiration
  • Chest X-rays
  • Feline leukemia virus test
  • Complete blood count
  • CT scan
  • Virus infection test

Chest X-rays can display swelling caused by the disease, often by affecting the lymph nodes near the origin of the mass. Aside from looking at the healthiness of lymph nodes, a complete blood count can detect the presence of cancerous cells as well. The complete number of white blood cells is an essential detail for veterinary professionals.

How to Treat Feline Cancers of Fibroblasts

Often, surgical removal is necessary for treating a tissue lump. Surgical removal of the cancerous tumor reduces the likelihood of recurrence and removes the uncomfortable lump from your pet's body. Keep in mind though that surgical removal of the tumor doesn't remove the chance of recurrence 100%. Excision often gets rid of the bad cells, but sometimes, surgery alone is not enough.

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In cases where excision surgery hasn't worked completely, and there is a chance of recurrence, it could be a good time to try radiation therapy. Radiation therapy works wonders as a treatment option. 

Radiation therapy is very effective when applied to tumors that are local. It's best to apply radiation therapy to situations where the cancer cells have not spread and grown out of control. As long as the cancer is under control, remission is likely.

Aside from surgery, radiation therapy is a way of being precise and targeting a tumor. Radiation therapy can either be used on its own or in tandem with surgery, but the decision about radiation will depend on veterinary professionals' input. In some cases, it is common for radiation therapy to follow chemotherapy as an additional treatment tool for removing the tumor, too. 

Chemotherapy is an exhausting process. While it is effective, the medicine takes a toll on your feline friend, both physically and mentally. When your pet undergoes chemotherapy, they will be very fragile and need extra love and attention.

Treatment options like radiation and chemotherapy can have margins of error, so they aren't always effective. Additionally, the goal is to a removed tumor with clean margins, meaning your feline friend won't have to undergo further treatment. If it isn't removed with clean margins, the second-best goal is to achieve adequate ones involving additional treatment options beyond a removed tumor.

How Long Can Cats Live?

Originating within the connective tissue, it starts out very aggressively. This means it's considered high grade. Once the high grade disease spreads throughout the tissues surrounding the origin site, the cancerous high grade cells pose a threat to your pet's well being because the tumor can spread.

The rate of surviving depends on the grade of the feline tumor. With a low grade tumor, the situation is less serious because the aggressiveness is not as strong as a tumor that is categorized as high grade. In other words, the lower the grade of sarcoma, the better.

However, once local tumors grow and spread, the speed at which the disease moves to other areas is far slower, which is another way of saying that this type of cancer is not as aggressive once they move beyond the initial area. 

Technically speaking, tissue tumors grow along feline tissue planes. These tissue planes act as a passageway for tumors to spread to other parts of the body more easily.

The local recurrence rate depends on the details of a cat's situation. The prognosis will vary based on the specifics of each situation. Generally speaking, about fifty percent of cats have a chance of survival. So there is a good chance of survival.

Thankfully, the chances of remission or survival can be increased by early detection. The sooner it is spotted, the more time the professionals have to figure out what is going on, the better the chance of survival.

Time is on your side when it is detected early because late-stage tumors are harder to treat. The goal is to catch the tumor in time so that the medical professionals can diagnose, treat, and monitor the situation.

Always check the injection site of vaccines in case a tumor starts growing. If tumors appear, keep an eye on its size and mention the presence of any tumor to a veterinarian. 

The tumor aside, be on the lookout for other symptoms as well. Make sure you reach out to your cat's vet immediately upon noticing any causes for concern. 


Feline Fibrosarcoma
Fibrosarcoma / Soft Tissue Sarcoma
What is Fibrosarcoma?
Radiation Theraphy and Surgery for Fibrosarcoma in 33 Cats
Injection-site Sarcomas in cats

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