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Feline Injection Site Fibrosarcoma

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Feline ‘Injection Site’ or ‘Vaccine Associated’ Fibrosarcoma is a rapidly progressive and aggressive tumour affecting cats.


On a deeply scientific level, 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. If this condition arises then we believe that the patient can have a realistic chance of a continued good quality of life provided that rapid appropriate action is taken.


If you detect a subcutaneous swelling in your cat at a possible injection site we advise that the following actions are taken:


  • Seek veterinary attention (soon, within the following two days)


  • The vet should evaluate and measure the lump. If the lesion is larger than 1cm across or appears to be rapidly growing the veterinary surgeon ought first to contact a veterinary oncologist in case there is updated advice to that which follows


  • If the lump is less than 1cm or appears not to be rapidly growing another evaluation should be made in 1 month


  • If the lump continues not to grow, continue monthly checks for 3 months in total. After this time decisions can be made between you and your veterinary surgeon about the most appropriate way to proceed, this may involve biopsy or removal.


  • 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.


It is generally well recognised by veterinary oncologists that surgery offers the best chance of long term control. This is rarely so, however, if the surgery is not performed by an appropriately trained soft tissue surgeon.


At Davies Veterinary Specialists we are currently employing a combination therapy approach which harnesses the benefits of both chemotherapy and surgery for what is proving to be an improved outcome for the patients concerned. Unfortunately, this treatment strategy is not appropriate for all patients. It is important that we fully evaluate patients first to ensure that we do not risk prescribing treatment that would not ultimately help the individual patient. Such an evaluation might alter the general advice given above.


If you are concerned about the health of your pet you should contact your veterinary surgeon.

Linnaeus Veterinary Limited trading as Davies Veterinary Specialists 01582 883950

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