We've just been to the vets and the vet says she thinks its her microchip, but when moving the device over her it was hard to pinpoint where it was as it beeped once on her neck but also beeped over her back! Im hoping its the chip - she's only been chipped 3 years, surely it wouldn't migrate that far down her back so quickly?

Anyway the vet recomended checking the size again in 2 weeks and bringing her back if it gets larger, so at least I know by waiting and watching I am doing the right thing.

Thankyou for the replies

Its no good, I am still worrying about this even though its christmas eve

After feeling around the area I think ive located her microchip, and it isn't this lump. Its much more 'rice' like and what I have felt in cats before. Its only been a few days since I noticed the lump so can't really tell if its getting bigger or not yet.

EVERYTHING I read about lumps in this area suggeste vaccina assosicated sarcoma I know you shouldn't read things on the internet, but the majority of these articles are based on truth and fact and that can't be ignored.

I hate this waiting game just waiting to see if it will get bigger, and am going to spend my christmas break worrying

something very similar happens to one of my two cats, I kept thinking it must be the microchip, but it did feel bigger than that and moved about, then I used to think it was a scab, it happened a couple of time that I realized it happened when? I used the flea drops on her in the same spot, it was a reaction to the flea drops, I thought I could get a flea collar for her, but I did not I was scared of her getting a reaction all around her neck area so I got a flea zapper its a comb which zaps the fleas as soon as it detects it I use it on both the cats they love it, I love getting the fleas zapped.