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Feline injection site sarcoma

Feline 'Injection Site Sarcoma' or 'Vaccine Associated Fibrosarcoma' is a rapidly progressive and aggressive cancer affecting cats. The true cause of the disease is not yet understood but it is definitely associated with the administration of long-acting injections like vaccinations. Vaccine technology has advanced since the condition was first reported in October 1991 and effective vaccinations now exist that have not yet been associated with this condition. Rapid appropriate action is required to give patients with this condition the best chance of a lengthy remission or cure.

Your questions answered

What is an injection site sarcoma?

Feline 'Injection Site Sarcoma' or 'Vaccine Associated Fibrosarcoma' is a rapidly progressive and aggressive cancer affecting cats. The true cause of the disease is not yet understood but it is definitely associated with the administration of long-acting injections like vaccinations.

How would I know if my cat has an injection site sarcoma?

Injection site sarcomas can develop in cats of almost any age - usually months or years after vaccination. They typically occur at he base of the neck between the shoulder blades as this is the site most commonly used for injection in cats. However, they may develop at any site where an injection has been given.
Usually the mass if the first sign noticed before the animal becomes ill in any other way.

What should I do if my cat develops a swelling on its neck?

If you detect a swelling under the skin in your cat at a site where they have previously had an injection seek veterinary attention straight away (within the following two days). Your vet will evaluate and measure the lump.

  • If the lump is larger than 1cm across or appears to be rapidly growing ask your vet to contact a veterinary oncologist to get up-to-date advice on treatment. For rapidly growing or larger lesions it is recommended that an incisional biopsy is taken in all cases. Attempted removal without knowing the true nature of the lump can foil all chances of a long term remission.
  • If the lump is less than 1cm or appears not to be rapidly growing it may be assessed again 1 month later. If at follow up examination it is apparent that the lump is not growing, continue monthly checks for 3 months in total. After this time decisions can be made between you and your vet about the most appropriate way to proceed, this may involve biopsy or removal of the lump.

Can injection site sarcomas be treated?

It is generally well recognised by veterinary oncologists that surgery offers the best chance of long term control. However, this surgery MUST be performed by an appropriately trained soft tissue surgeon and it is likely that your cat would need to be referred to a specialist centre to get the most effective treatment.

Specialist oncologists may offer a combination therapy approach which harnesses the benefits of both chemotherapy and surgery to provide a dramatically improved outcome for the patients concerned. Unfortunately, this treatment strategy is not appropriate for all patients. It is important that patients are fully evaluated first to ensure that treatment is not prescribed to patients that would not ultimately benefit from the treatment plan offered. As always, the goal of therapy is first and foremost to extend a good quality of life, not to attempt to extend life at all costs.

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