A little swelling after vaccination or an injection is normal. However, if the swelling does not go away and tends to get bigger, it should be examined by your vet. In the worst case, it could be an Feline injection site associated sarcoma (FISS) act.

How does FISS develop in cats?

The FISS is a Connective tissue tumor, which can develop on part of the skin in the cat injected a few months or years earlier has been. FISS develops relatively rarely, it is estimated that only one to four vaccinated cats in 10,000 develop.

Affected cats usually get sick at the age of from eight to twelve years but it can also be younger in individual cases. Little is known about the causes of FISS. Chronic inflammation is believed to damage connective tissue cells in such a way that they degenerate into cancer cells.

It triggers inflammation could be:

  • Injuries
  • Foreign body
  • Insect bites
  • Side effects from vaccinations or drug injections

However, since fewer than one percent (0.01 to 0.04 percent) of cats develop FISS after an injection, there is a high probability that affected animals also have a hereditary predisposition to developing cancers.

When stroking yourself you should beware of swelling. © Stock.adobe.com/Anna Ritter

Risk factors for the development of FISS

What factors favor the development of FISS? There are many studies on this. So far the following factors have been documented:

  • Number of injections in one place: more injections, higher risk.
  • Location of the puncture site: If the injection is given between the shoulder blades, the risk of FISS is greater.
  • Temperature: If the injection solution is colder than room temperature, this affects the risk of inflammation at the injection site.
  • Use of adjuvants (eg aluminum salts): These are stimulators of active ingredients in vaccines used to enhance the immune response.
  • Hereditary factors: One study showed a higher risk in siblings of cats with FISS.

This is how long you should be looking at puncture sites

The American Veterinary Society AVMA recommends Check vaccination or injection sites for a few weeks after treatmentin order to identify changes in these areas at an early stage. If the swelling at the vaccination site, which is completely harmless in most cases, tends to increase or does not go away during this time, it should be examined by a veterinarian.

Older cats, who generally have an increased risk of cancer, should be checked regularly for swelling under or under the skin. If you discover a small swelling or lump, you should note the date it was found, the body part affected, and the size of the small lump. Voices help enormously in quickly recognizing whether swelling is gradually increasing or showing other changes.

In case of tumors larger than one centimeter in diameter, consult a veterinarian immediately.

A tumor must be surgically removed. © Stock.adobe.com/feferoni

Prevent the development of FISS

Unfortunately, there is no one hundred percent protection against the development of a FISS. But there are expert recommendations on how to reduce the risk of developing FISS:

  • Vaccinate – as much as necessary, as little as possible.
  • Vaccinate or inject only on parts of the body where a tumor can be easily removed.

The health risks from poor vaccination protection or neglect of important care are much greater for the cat than the risk of developing FISS.

The cat has FISS – how to treat?

If FISS is suspected, your vet will do so Fabric samples and have it examined under a microscope by a special laboratory to rule out other causes of the tumor. If there are degenerated connective tissue cells in the tissue sample, this supports the suspicion of FISS. However, the vet can only make a definitive diagnosis after the tumor has been removed and examined as a whole.

The more the FISS has grown into the surrounding tissue, the worse the chances of eventual healing are. However, cats can depend Severity of the tumor disease have a good life for a while with proper care and care. However, as soon as the animal suffers and no longer responds to treatment, a sweet and painless death should be allowed.


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