I can just pass on the info I was given when Swampy had to have a lump removed after a rabies jab in 2005. It didn't go down after 2 months, it felt fibrous so I was terrified of fibrosarcoma. He had it removed and the lab report was "benign, but watch the site, don't inject there again". At the time I had long email correspondence with 2 of the UK and EU's best cancer specialists who told me that
- only vaccinate if the benefit outweighs the risks (outdoor cat or in contact with outdoor cats: leukaemia risk) or the law requires it (eg rabies) and vaccinate in the leg and in a different site each time (and keep a note of where);
- use the vaccines that only have to be repeated every 3 years if possible (rabies); (for the others you could always try to measure the antibody titration in the blood to see if there was still some protection I suppose);
- the vaccines that cause fibrosarcoma tend to be those against rabies and leukaemia; not the flu ones
- it's the adjuvant in the vaccine (aluminium which is put in to trigger an immune response) that causes it
- wait and see a reasonable time if the lump goes down as very often they do and no further action is necessary - or the lump may become less suspicious so the op to remove it is an ordinary lumpectomy (which Swamp had) not the bigger op required if they think it's fibrosarcoma;
- if a cat has had a lump once as a response to a vaccine, that cat is predisposed to getting other lumps in future if vaccinated. (EU specialist favours using different sites for ordinary injections in lump-predisposed cats);
- the fine needle biopsies are not totally accurate. (Swampy had one and an ultrasound, both of which did reassure the surgeon though)
- if you do vaccinate, choose a site where lump removal can be done fairly easily ie best to avoid between the shoulder blades. That is why the advice - as you know as you had it done - is to do it in the leg (although that is a totally gruesome thought isn't it, but the cat would survive).
If you are really worried and want a specialist referral, I would highly recommend Davies in Hertfordshire. Their head oncologist was so very kind to me and I wasn't even his client nor Swampy his patient at the time. You are not worrying about nothing, I know how desperate I was that it may be fibrosarcoma, especially as the lump felt fibrous. Cats get a lot of benign lumps as a result of vaccines. I really hope the lump just goes down - Swampy had to have another rabies one (in the leg) btw and another little lump grew and it DID go down. How long has he had the lump for?
All the very, very best and try not to worry too much
