Cancer is a sad subject, but one that needs to be addressed. If your pet gets a diagnosis of cancer, being educated on the treatment options could make a big difference in your pet’s life.

In this blog, we’ll discuss locally invasive tumors, which work a bit differently than what we typically think of as cancer. Locally invasive tumors, like fibrosarcoma and squamous cell carcinoma, grow in one place and tend to not spread until late in the disease course, if they spread at all.


Our feline friends are particularly prone to developing fibrosarcoma, which arises from soft tissues in cats. While it looks like a discrete round tumor, in this case, looks are deceiving. The tumor actually has hundreds of finger-like projections, or tendrils, that invade the surrounding soft tissue and extend well beyond the margins of the visible tumor.

When trying to surgically remove a fibrosarcoma, these tendrils must be taken into account. Leaving any tumor cells behind will result in regrowth of the mass. Often, when a fibrosarcoma is surgically removed, it will regrow even more aggressively.

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What causes Fibrosarcoma?

Fibrosarcomas can occur spontaneously or can be induced by the feline sarcoma virus. In addition, evidence exists to suggest that routine vaccination is another cause. The incidence of this occurring is rare, with only one in 1,000 to one in 10,000 cats developing vaccine-associated fibrosarcomas.

This news may make you think again about vaccinating your cat against common diseases, but don’t! You should still be vigilant about ensuring that your cat’s vaccinations are up to date, but you and your veterinarian should develop a plan to vaccinate in a smart way.

  • Discuss your cat’s lifestyle and avoid unnecessary vaccines.
  • Be sure your vet vaccinates your cat in standard areas – there is a standard location for each vaccine.
  • Vaccinating low on the limb, rather than between the shoulder blades, makes the likelihood for complete surgical removal of possible fibrosarcomas better.


Once a fibrosarcoma is detected, surgery to remove the tumor is generally considered. Very wide margins must be obtained in order to remove the entire tumor, so the incision will appear quite large. Though chemotherapy is not thought to be very effective against fibrosarcomas, radiation therapy is helpful to prolong the disease-free interval and can be covered by your Petplan pet insurance plan.

Nov 28, 2011
Pet Health

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