4 Things You Should Know About Feline Fibrosarcoma

Feline fibrosarcoma is a rare cancer in cats, accounting for a small percentage of all cancers in this species. However, fibrosarcoma is the most common type of soft tissue cancer in cats. It is of mesenchymal origin and mainly affects the fibroblast cells in the connective tissue.

They are locally aggressive, malignant cancers that have a high incidence rate after surgical removal. However, the rate of spreading to other organs and tissues (metastasis) is low.

Fibrosarcoma generally occurs in adult cats between the ages of 6 and 12 years. Clinical signs may include lumps (everywhere on the body), hair loss, skin changes, hair discoloration, etc. In some cases, the tumor may ulcerate. There is also post-vaccination fibrosarcoma, which occurs in some cats due to repeated vaccination in the same place.
In this article, we will talk about the types of fibrosarcoma in cats, what you need to know about this condition, the clinical signs, the stages of fibrosarcoma, and much more.

What Is Feline Fibrosarcoma?

Feline fibrosarcoma is a malignant cancer of fibrous connective tissue. It is often found in older cats, the mean age being 9.6 years. It is characterized by aggressive local growth and a low tendency to spread to other organs or tissues.

It occurs most often on the skin or subcutaneously, especially on the back, limbs, and sides of the body (flanks).

The prognosis may vary depending on the size of the tumor and the possibility of complete surgical removal (excision).

4 Things You Should Know About Feline Fibrosarcoma

1. Vaccines and injections can be a risk factor.

In some cases, when repeated vaccinations or injections are given at the same site, post-vaccination sarcomas (mostly fibrosarcomas) can occur. This can happen because repeated inflammation at the injection site can trigger abnormal cell growth, leading to tumor formation.

To reduce this risk, veterinarians follow certain vaccination and injection protocols, such as avoiding repeated injections at the same site and choosing areas of the body where surgical removal of the tumor can be easily done, if necessary - the interscapular region (between the shoulder blades) should be avoided.

2. Feline fibrosarcoma is an aggressive soft tissue tumor.

Feline fibrosarcoma is a type of cancer in cats that arises from the fibroblast cells of the connective tissue. It is a locally invasive cancer, meaning it aggressively infiltrates the surrounding tissues. It rarely metastasizes but has a high recurrence rate even after treatment.

3. Recurrence is common, and treatment may require multiple approaches.

Even if the tumor is surgically removed, it often recurs within a few months following surgery. Therefore, for better cancer management and prolonging the cat's life, the vet may recommend combining surgical removal with other conventional treatment methods, such as radiotherapy and chemotherapy. In addition, regular check-ups and monitoring of the cat for tumor recurrence are essential for long-term disease management.

4. Early detection and surgery improve prognosis.

Successful treatment involves early detection of feline fibrosarcoma. Clinical signs may include a firm, rapidly growing lump or bump under the skin (often at the site of a previous injection or vaccination).
Although surgical removal is the treatment of choice, wide surgical margins (with healthy tissue) are necessary to ensure that all tumor cells are removed, thereby decreasing the risk of recurrence. In some cases, in addition to surgical removal, chemotherapy or radiation therapy is also needed to reduce the risk of recurrence.

Feline Fibrosarcoma Types

There are three types of feline fibrosarcoma in cats. They can be classified depending on the cause, location, and biological behavior of the tumor. Here are the types of fibrosarcoma in cats:

1. Post-vaccination fibrosarcoma

As previously mentioned, this type of fibrosarcoma is associated with repeated injections or vaccinations in the same spot. According to studies, the most common vaccines used that can lead to post-vaccination fibrosarcoma are rabies and feline leukemia virus (FeLV).

It occurs rarely in cats (1 case in 10,000-30,000 vaccinations) and has distinct characteristics from other fibrosarcomas that occur in other areas of the body. The time of occurrence of post-vaccination fibrosarcoma is between 3 months and 4 years after vaccination. In some rare cases, post-vaccination fibrosarcoma can occur even 5 years after vaccination.

In 14-22% of cases, it can recur at the original site, even with complete surgical removal of the tumor. In cases where the surgical removal was incomplete, the chances of recurrence are higher (56-69% of cases).

2. Spontaneous fibrosarcoma

This type of fibrosarcoma is not contagious and occurs spontaneously, and is not associated with repeated injections or vaccinations in the same place. As a result, there is no way to prevent it. It can appear anywhere on the body.

According to studies, this type of fibrosarcoma occurs less frequently than post-vaccination fibrosarcoma, its development being associated with genetic changes.

It has a lower development rate compared to post-vaccination fibrosarcoma, but can recur locally.  As a result, monitoring your cat's overall health is important to detect any abnormalities early. This way, treatment can be started as soon as possible, increasing your cat’s chances of survival.

Oral fibrosarcoma in cats is an aggressive malignant tumor that affects the soft tissues of the oral cavity. It is the second most common oral tumor in cats, with an incidence of 13%-17%. It can be difficult to treat due to its high recurrence rate. Local invasion and bone involvement are common.

3. Virus-associated fibrosarcoma

The most common virus involved in the occurrence of this type of fibrosarcoma is the Feline Leukemia Virus (FeLV).

Infection with this virus leads to the development of fibrosarcomas by combining FeLV proviral particles with proto-oncogenes in the infected cat's genome, which leads to oncogenic mutations - proto-oncogenes are genes that, when mutated, can transform normal cells into cancerous ones. FeLV combined with proto-oncogenes leads to feline sarcoma virus, which is a hybrid virus. As a result, all cats with fibrosarcoma of viral origin are always positive for FeLV. This type of fibrosarcoma is not transmitted to other cats.

Spread to other organs or tissues occurs in approximately 30% of cases and generally affects the lungs, and the prognosis is reserved.

Cats infected with FeLV have a higher risk of developing multicentric fibrosarcomas. Feline multicentric fibrosarcoma is a rare and aggressive form that is characterized by the appearance of multiple tumors simultaneously, affecting various regions of the cat's body. It affects young cats, up to 4 years old.

In addition, some cats with FeLV may also be infected with the Feline Immunodeficiency Virus (FIV), which weakens their immune system even more, favoring the development of cancer, including fibrosarcomas.  

4. Primary intraosseous fibrosarcoma

This type of fibrosarcoma is very rare in cats. It develops in the bones and usually affects the limbs. As reported in one case, a cat presented to the clinic with a hump on the right forelimb. X-rays revealed a well-defined osteolytic lesion at the elbow joint. The affected limb was amputated, and histological analysis confirmed tumor invasion into local veins and metastases in the axillary lymph nodes. One year after surgery, the cat showed no signs of tumor recurrence or pulmonary metastases.

Clinical Signs Of Feline Fibrosarcoma

The clinical signs of feline fibrosarcoma can vary depending on the location, size of the tumor, and the presence of metastases. Here are the symptoms associated with this condition:

1. Local signs

You may notice a firm, fixed, or slightly mobile, subcutaneous or cutaneous nodule or tumor mass of variable size. It grows rapidly and can become large in a short time. You may also notice ulceration and bleeding, especially in advanced stages. In these cases, the skin over the tumor may break, leading to ulceration and secondary infections.
You may also notice local inflammation and redness. In addition, the nodule may be painful, especially if it invades surrounding tissues (nerves or bones).

2. Systemic signs (if the fibrosarcoma has spread far in the body or has a high degree of local extension)

In this case, you may notice the following:

• Poor appetite
• Weight loss
• Lethargy
• Trouble breathing, especially in the case of pulmonary metastases
• Trouble walking when joints or bones are affected.

3. Clinical signs depending on the type of fibrosarcoma

• Cutaneous and subcutaneous fibrosarcoma: firm, ulcerated, or non-ulcerated mass, frequently located on the head, neck, trunk, or limbs.
• Post-vaccination fibrosarcoma: occurs at the site of repeated injections and vaccines in the same place, grows rapidly, and can infiltrate adjacent tissues
• Bone (intraosseous) fibrosarcoma: severe pain, progressive lameness, pathological fractures, and local inflammation.

4. Clinical Signs Associated with Viral-Induced Fibrosarcoma (Feline Sarcoma Virus)

Here’s what you may notice:

• Multiple skin nodules (multicentric fibrosarcoma)
• Occurs in young cats
• Lesions at bite sites (sometimes)
• Poor response to treatment

Early diagnosis and aggressive treatment are essential to improve your cat’s prognosis and survival time. Therefore, if you notice clinical signs or behavioral changes, it is advisable to take your cat to the vet as soon as possible for a proper diagnosis.

How Do Veterinarians Diagnose Feline Fibrosarcoma?

Diagnosing feline fibrosarcoma requires (like any other type of cancer) a complex approach that includes several steps and diagnostic methods. As a result, here is how veterinarians can diagnose feline fibrosarcoma:

1. Physical examination

The physical examination includes palpating the node(s) to determine certain characteristics such as firmness, mobility, size, and possible ulceration. The veterinarian will then check the regional lymph nodes to see if the cancer has spread locally.
The veterinarian will also evaluate your cat to see if they have lost weight, are lethargic, and if they have difficulty walking or breathing.

2. Blood tests

Your veterinarian will recommend a set of blood tests to see how your cat's internal organs are functioning. In addition, they may also recommend a rapid test for the feline leukemia virus - as mentioned earlier, FeLV is responsible in some cases for the appearance of feline fibrosarcoma.

3. Imaging

Imaging is essential to assess the extent of fibrosarcoma and possible metastases. It may include: X-rays, abdominal ultrasound, MRI, and CT.

Radiographs

X-rays can detect bone fibrosarcomas or if the cancer has spread to the lungs.

Abdominal ultrasound

This helps evaluate the soft structures of the body and identify abdominal metastases.

Computed tomography (CT) and magnetic resonance imaging (MRI)

Both imaging methods are superior to radiographs. They help determine the size of the tumor and more accurately assess the extent of the disease.

3. Cytological diagnosis

Sample collection for cytological diagnosis is done by fine needle aspiration (FNA). This is a minimally invasive method that involves inserting a fine needle into the nodule and aspirating tumor cells, which will then be examined under a microscope for diagnosis. In some cases, the diagnosis may be inconclusive and the veterinarian may recommend a new collection by FNA or biopsy.

4. Histopathological diagnosis

A biopsy is required for histopathological diagnosis. This is an invasive method that involves removing a fragment of tumor tissue (partial biopsy) or the entire tumor (total biopsy), which will then be analyzed under a microscope. Histopathological diagnosis can also help establish the degree of malignancy of the tumor.

5. Immunohistochemical tests

Immunohistochemical tests are used to differentiate fibrosarcoma from other types of sarcomas and to investigate the cause of the tumor. Specific markers are used for these.

How Do Veterinarians Treat Feline Fibrosarcoma?

As with most types of cancer, the treatment of feline fibrosarcoma is complex and involves multiple treatment methods. These methods depend on certain factors such as the size, location, and degree of malignancy of the tumor, the presence of metastases, and the general health of the affected cat. So, here are the treatment methods for feline fibrosarcoma:

1. Surgery

Surgical removal is the treatment of choice for feline fibrosarcoma. This treatment method can be used for small to moderate, well-demarcated nodules without significant local invasion or obvious metastases.

Veterinarians recommend complete excision of the tumor with wide margins (3-5 cm) around the tumor to ensure that no tumor cells remain. In cases of intraosseous fibrosarcoma, amputation of the affected limb is necessary.

If complete excision is not possible, postoperative radiotherapy is recommended.

Postoperative recovery may include monitoring the wound for surgical site infection or recurrence and administration of pain medications and antibiotics.

Feline Fibrosarcoma Life Expectancy

Surgical treatment alone has a high risk of recurrence. Life expectancy is 1-2 years if the tumor is completely excised with wide margins.

When used together with radiotherapy, life expectancy increases (3-4 years), and the risk of recurrence decreases.

In the case of metastatic tumors, life expectancy is very low, somewhere around 3-6 months.

2. Radiotherapy

This is recommended when the tumor cannot be completely removed by surgical excision or if the tumor is in a difficult-to-operate area (e.g., head).
Multiple sessions are usually recommended for increased efficiency. Radiotherapy can reduce the risk of tumor recurrence.

3. Chemotherapy

Feline fibrosarcoma is relatively resistant to chemotherapy. However, it may be recommended in advanced or metastatic cases in combination with radiotherapy and/or surgery. If the owner does not want radiotherapy or surgery, the vet may only recommend chemotherapy.

4. Symptomatic treatment

Symptomatic treatment aims to manage pain and improve quality of life. A diet rich in protein and omega-3 fatty acids may also be recommended as it can reduce inflammation and support the cat's immunity to better fight the disease.

What Is The Prognosis Of Feline Fibrosarcoma?

Certain factors influence the prognosis of feline fibrosarcoma, such as:

• Size and location of the tumor – small, operable tumors have a better prognosis than large, inoperable ones.
• Degree of surgical excision – the wider the safety margins, the better the prognosis because the risk of recurrence decreases.
• The use of postoperative radiotherapy decreases the risk of recurrence.
• Presence of metastases – when metastases are present, the prognosis is reserved because they decrease life expectancy.

Is There Any Natural Treatment For Feline Fibrosarcoma?

Some natural remedies or products can help your cat with feline fibrosarcoma fight the disease better. These products usually strengthen your pet’s immune system, enhancing their overall well-being. They are also considered a gentler approach to conventional treatments.

Such products are PIPTOPET, TONICPET#4, #5, #7, and #10 from Zumalka.

PIPTOPET is a mother tincture that can support cats in their fight against fibrosarcoma. The main ingredient in this product is Fomitopsis betulina, also known as birch polypore, which is a medicinal mushroom known for centuries for its beneficial properties. Studies performed on various animals showed their multiple benefits. Therefore, it has antibacterial, antiviral, antitumoral, anti-inflammatory, immune support, and antioxidant properties.

It is an excellent product for cats with fibrosarcoma because it promotes the natural healing responses by supporting the immune system. If you want to complement PIPTOPET’s properties, you can add to your sick cat treatment the following natural products:

TONICPET #4, TONICPET #5, and TONICPET #7: These tissue salts help promote healthy oxygen circulation and support normal inflammatory responses, contributing to overall tissue balance. Maintaining healthy tissues is essential for overall well-being.

TONICPET #10: It helps support a balanced internal environment by promoting normal pH levels. A well-balanced pH is important for maintaining overall health and proper cellular function.

Using natural products can help promote healthy circulation, support your cat’s natural immune function, and contribute to their overall comfort and quality of life in their fight against cancer.

Frequently Asked Questions (FAQs)

How Long Will A Cat Live With Fibrosarcoma?

The survival time of cats with feline fibrosarcoma depends on several factors such as tumor size, location, stage, distant spread, and the cat's general health. As a result, if the cat is left untreated, the survival time can be several months. If surgical treatment is chosen, the survival time is 1-2 years. If radiotherapy is added after surgical removal, the survival time can increase to 4 years. In the case of metastases, the survival time is only a few months.

What Is The Life Expectancy Of A Cat With Sarcoma?

Survival time for cats with sarcoma can range from a few months to a few years, depending on several factors. As a result, the size, location, and stage of the tumor influence survival time. As well as the treatment and the cat's general health.

How Much Does It Cost To Treat Fibrosarcoma In Cats?

Treating fibrosarcoma in cats can be quite expensive, often surpassing $10,000, because it requires specialized surgery, chemotherapy, and/or radiation. The cost of an initial diagnosis is usually under $500. Additional tests to determine the extent and location of the tumor can cost up to $2,000. Surgery can cost up to $3,000, depending on tumor size and the surgeon's expertise. Chemotherapy expenses usually range from $1,000 to $5,000, while radiation can cost between $5,000 and $10,000. The overall cost of treatment varies based on factors like location, the level of care provided.

What Is The Survival Rate For Fibrosarcoma?

The survival rate for cats with fibrosarcoma is a few months to a few years and depends on the size, location, and stage of the tumor, as well as the cat's general health and whether or not treatment is chosen. Therefore, cats that undergo surgery and radiotherapy have an average survival time of 2-4 years.

What Is The Prognosis For Oral Fibrosarcoma In Cats?

The prognosis for oral fibrosarcoma in cats is generally guarded. If the tumor is completely removed with clean margins, the cat can survive for 1 to 3 years, although some may live longer if there is no recurrence or metastasis. However, if the tumor has spread or cannot be completely removed, the prognosis becomes poorer and the survival time is shortened.

How Long Can A Cat Live With Oral Cancer?

Depending on the type of tumor, size, location, and stage, as well as the treatment chosen and the cat's overall health, pets with oral cancer can live from one day to five years after diagnosis. So, whenever you notice that something is wrong with your cat, take them to the vet for diagnosis and treatment.

What Does A Feline Fibrosarcoma Feel Like?

Fibrosarcoma presents as a skin lump or mass that doesn't seem to cause the cat pain. In addition, it can also occur in the mouth or intraosseous. There is also multicentric fibrosarcoma, where multiple nodules appear on the cat's skin.

About the author

Dr. Iuliana Mihai, DVM, MSc, PhD

Iuliana Mihai, DVM, MSc, PhD, is a Bucharest-based veterinary expert specializing in internal medicine and oncology.

Her work has been published in reputable publications such as Veterinary Medicine Journal, Catster.com, Dogster.com, Hepper.com, Meowiz.com, Springnaturals.com, Petkeen.com, and Wilderharrier.com.

She is a malpractice and negligence veterinary consultant and a graduate of The University of Agronomic Sciences and Veterinary Medicine and The Romanian Academy.

Read the complete profile of Dr. Iuliana Mihai, DVM, MSc, PhD (Veterinarian) here.