What is Fibrosarcoma?
When describing feline fibrosarcoma, vets explain that this type of cancer begins in individual cells within connective tissue, as well as just under the surface of the cat’s skin.
Fibrosarcoma is a form of soft-tissue cancer that is common to cats. Fibrosarcoma is aggressive in the cells where it first appears, but slow to spread to other body organs or systems. Fibrosarcomas begin in the fibroblasts of the skin (cells in connective tissues) and in subcutaneous (under the skin surface) connective tissues. While some grow slowly, others may grow more quickly. After being surgically removed, fibrosarcomas can grow back. This type of tumor is most often caused by papillomavirus, the virus that causes warts.
Symptoms of Fibrosarcoma in Cats
The cat’s owner is most likely to notice lumps just underneath the surface of the cat’s skin. These lumps can appear anywhere on the cat’s body: the head, legs, in the mouth and anywhere else on its body. Other symptoms include:
- Lumps may be fleshy or firm
- The cat may not feel pain from the lumps
- Lumps are irregularly shaped
Fibrosarcomas can also develop inside the cat’s body; usually on its spine, in the pelvis, or in its ribs. Advanced fibrosarcoma causes the cat to:
- Have difficulty eating
- Lose its appetite
- Become dehydrated
- Painful walking
- Become lethargic
- Develop mysterious bleeding in its mouth
Causes of Fibrosarcoma in Cats
Cats can develop fibrosarcoma for one of three reasons. If the cat is older, it may be more prone to developing this particular form of cancer.
Some vaccines have been linked to the development of fibrosarcoma, but these occurrences are rare. When fibrosarcoma develops as the result of vaccinations, it is called “vaccinosarcoma” or vaccine-induced sarcoma. While vets still recommend that cat owners have their pets vaccinated, vets will give one vaccine, such as the rabies shot, in one leg, then give the feline leukemia (FeLV) vaccine in the opposite leg.
The adjuvant within the vaccination is usually aluminum. This ingredient helps to keep the killed virus within the area where the injection was given for a short time so the body can develop an immune response. By keeping the killed virus in one small area, it makes it easier for the cat to develop a localized inflammation, which can stimulate the development of the sarcoma. Cat owners should discuss modifying their cat’s vaccination schedule with the vet.
The third cause is a mutant form of FeLV, called feline sarcoma virus or FeSV, which can lead to fibrosarcoma. This occurs in younger cats, who develop multiple tumors.
Diagnosis of Fibrosarcoma in Cats
If the vet suspects a fibrosarcoma, they will run several tests. First, they will give the cat a full physical exam, from head to tail, so they can rule out any other causes of the lumps. Making an early diagnosis while the cancerous lump is still small gives the cat a higher chance of recovery and survival. Early detection also allows the vet to prescribe more options that give the cat a more positive outcome.
They will order routine testing, such as a biochemical profile, urinalysis and a complete blood count. These tests allow the vet to rule out other illnesses, other than a low lymphocyte count.
Next, the vet will order X-rays or a CT scan, which allow them to see the lump and whether the cancer has spread to other parts of the cat’s body. An X-ray shows a fibrosarcoma as a soft tissue mass.
Once the vet begins to narrow their diagnosis down, they will do a fine-needle aspiration or biopsy of the lump so the cells can be examined under a microscope.
Finally, the vet does a FeLV test. This will allow them to determine if the fibrosarcoma has developed because of FeSV.
Once the vet has made a diagnosis, the pet owner will need to work with them to start cancer treatment and begin an at-home treatment regimen so the cat has a better chance of survival.
Treatment of Fibrosarcoma in Cats
Treatment options depend on where in the cat’s body the cancer is located. It’s much easier to treat cancer that has not spread to other organs, because they spread with nearly invisible tentacles. This makes complete eradication of the cancer even more difficult because, if any cancer cells remain in the cat’s body, new cancers can develop.
Depending on where the cancer is located, the vet may suggest surgery to remove the cancer, along with the removal of some of the healthy tissue. Limb amputation may be necessary.
Post-surgery, the vet may prescribe radiation, which helps to destroy any remaining cancerous cells. Radiation treatment begins about two weeks post-surgery.
Chemotherapy may also be prescribed. This can begin before surgery so the tumor can be shrunk, making removal easier. After surgery, chemo may be given again so remaining cancer cells can be killed off. While humans are likely to lose their hair, chemo given to a cat doesn’t lead to them losing their hair. Instead, it will be tired, sleeping more than usual for a day or two.
The vet may also recommend a combination of surgery, radiation therapy, and chemotherapy. When a cat with fibrosarcoma has undergone chemo, it may survive for two or three years after diagnosis and treatment.
The vet may opt for oral medication to treat the cancer. If the cat experiences pain symptoms, the vet prescribes pain medication. Some vets are open to complementary treatments, including immunotherapy, acupuncture or nutritional therapy.
Recovery of Fibrosarcoma in Cats
Recovery from fibrosarcoma depends on where the tumor is located, how long it has existed in the cat, and its grade. The grade is determined by the frequency of cell division within the tumor.
Very young cats (up to one year old) are more likely to have malignant tumors. If the cat dies from fibrosarcoma, it is likely because of the recurrence of primary site tumors. A veterinary pathologist can give the vet and cat owner a prognosis which gives the cat owner a probability of recurrence of the cancer or a metastasis of the cancer to other parts of the cat’s body.
At home, pet owners need to keep the cat from scratching, biting, licking or rubbing the tumor. If an affected area becomes ulcerated, the cat’s owner needs to keep this clean. After surgery, the cat owner should report any suture loss, swelling and bleeding to the vet.
Fibrosarcoma Questions and Advice from Veterinary Professionals
I just had a mass removed off my cats back leg. The mass was fairly big (cherry tomato size or a bit smaller) I only noticed it a month ago and took her in. They biopsied it and it came back fibrosarcoma. I’m still a little shaken and don’t understand it fully, but the vet is saying we need to move fast as this is a very aggressive form of cancer. She gave me options of chemo,radiation, or altogether amputating the leg. I’m not sure if I should take any of these actions seeing as we removed it and my cat has no other symptoms. Did I do the right thing removing it, should I go on with the treatment options.
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Hey there, Jolandie here.
My cat was diagnosed with gingivitis, and he got a Colvisone and Depo-Medrol injection.
Literally that same night, I felt a tiny lump against (Stuck) to is spine, or shall I say muscle. not sure, its definitely attached. just not sure to what, however it is close to the lower lumbar region on the left side. (IT'S NOT AT THE INJECTION SITE WHERE THIS BUMP APPEARED)
It is now almost 2 weeks later and it has grown to the size of say a cherry tomato/olive.
He does not seem to have any pain there (he sometimes jumps but im not sure if its because its painful), but I have noticed a change in his attitude lately. He also seems a tiny bit reluctant to move, besides for when it comes to food (he will run up and down following me and meowing for it).
Any idea what this could be?
He is going to the vet on friday. I am a very worried Cat mommy.
Hope someone can help.
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We are waiting on a diagnosis from our vet but is seems likely my 13 yr old male cat has fibrosarcoma. We have no idea how long it has been there - it is not a normal area that is pet out touched or seen. It is a hard, elongated large mass on the upper rear of a back leg. The vet said that amputation could be a likely requirement. We are not wanting to do that, or treat with chemo etc. So the question...if we wait and see how this goes, and it eventually breaks through the skin, can surgery be used to remove a majority of the mass and re-seal the skin to give him more time, or oncee it breaks through the skin you can't do much? Or, if that is our plan, would a surgery to reduce the size earlier be better? We will be able to talk to our vet next week in more detail, but I ran across this site and thought I would see if you could advise.
I would recommend operating (if you want to operate at all) now rather than later as the size would be more manageable and if the skin becomes involved you may end up with a wound with no excess skin to close up. Waiting it out isn’t really an option and it is better to address the problem now than a larger problem later on. Obviously each case is different and your Veterinarian will give you options about Mox’s specific case. Regards Dr Callum Turner DVM
My 4 year old cat has advanced fibrosarcoma on his left hip. He is a large cat and moves around well. However, he's recently started breathing heavy because of stress or pain. The tumor hasn't broken through the skin. He is a medium hair length cat and the tumor is somewhat hidden besides for the obvious asymmetry. His vet put him on gabapentin and he is resting and breathing at a normal rate now. I dread what comes next.
My cat was diagnosed with a fibrosarcoma about 6 months ago. It was surgically removed, but now it seems she has another 2 masses the same size as the previous fibrosarcoma on the same side as the previous one, along with that she has a mass of tiny lumps right down her spine, guessing that they too are fibroscarcoma's. I do not wish to put her through either chemo or radiation treatments. How long does this awful condition last before it claims lives?
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