Feline Sarcoma & Cysts in Cats

If Kitty develops a lump at an injection site, call your vet.
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It's important to keep Kitty's vaccinations up to date to protect him from disease. A tiny percentage of felines develop a cancer called feline sarcoma at vaccine injection sites. The risks of contracting potentially fatal illnesses far outweigh the chance of feline sarcoma, but check Kitty for lumps where he received shots.

Soft Tissue Sarcomas

To envision the way a malignant soft tissue sarcoma grows, think of a tumor with tentacles. This type of cancer tends to be aggressive, so once it's discovered time is of the essence regarding treatment. Also known as fibrosarcomas, they can form as a result of a cat's exposure to the feline sarcoma virus, usually occurring in younger felines. Cats can also develop sarcomas even if they haven't been exposed to the virus, but the most common cause of this cancer results from tumor formation in a cat's soft tissues at a vaccination site.


While it's not unusual for Kitty to develop a bump at an injection site, it should disappear within a couple of weeks. According to the American Veterinary Medical Association, if the lump persists for more than three months after the injection, grows in size, or the diameter is greater than 2 centimeters, take Kitty to the vet. Some vaccine-related sarcomas don't appear until years after the inoculation, and non-vaccine-related sarcomas also appear as bumps. Check Kitty regularly for any lumps and bumps and notify your vet if you find anything suspicious. Don't panic -- it could be a cyst, which is usually not serious.


Since the majority of feline sarcomas are vaccine-associated, veterinary associations developed guidelines for where felines should receive injections. Because the rabies and feline leukemia vaccinations are the most likely to cause sarcomas, the former is given in the right rear leg and latter in the left rear leg. If Kitty develops a sarcoma from one of those injections, amputating the limb can save his life. If the cancer has spread, surgery, radiation and chemotherapy may be in order.


If Kitty develops a cyst near the injection site, it's probably not a sarcoma. However, you can't tell if a lump is a cyst or tumor without having the vet check it out. A cyst contains a secretory lining, according to VCA Animal Hospitals. That means the membrane in its surface creates secretions, or the cystic material. Cysts generally form in glands because of blocked ducts. In order to rid the cat of the cyst, it's not enough simply to open it and remove the cheesy, cystic material. It's not a giant zit. The vet must remove the cyst surgically, or else the cystic membrane will continue to emit secretions.

Always check with your veterinarian before changing your pet’s diet, medication, or physical activity routines. This information is not a substitute for a vet’s opinion.

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