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Microchip Lump?

Nailah was microchipped when she was spayed May 14th. She now has a lump a little larger than a marble at the site. Is this normal? My vet says that sometimes they rarely develop fibrous tissue around the chips but I just wanted to see if anyone has had the same "reaction?" I know some of you breeders probably have a lot more experience with these microchips. Are there any known adverse reactions to these chips? My vet says he's never seen any which only makes me wonder.


Savannah Super Cat
Are you sure it is the chip and not the vaccine? Did she have a vaccine there? Rabies? The dog rabies? I would certainly double check that is a chip and not a injection site carcinoma? The use of dog rabies in cats can cause a lump or tumor. I had one that developed a lump that eventually disappeared but if it starts to grow, I would be very concerned. I doubt that it is from the microchip unless she has formed scar tissue around it. Better safe than sorry. I have never had that with a microchip nor seen one in all my year past experience at the vet.

Per Lausund

Staff member
If she has a lump the size of a marble where the id-chip was injected or where a vaccine was given you need to get your vet (the same as chipped her?) to have another look. The following possibilities , in order of probability, are some of the things you could find:
Infection at the site of the chip, possibly with a slow granuloma formation around the chip
Reaction to hair being brought in with the chip when she was chipped, giving a foreign-body reaction (very like a granuloma)
Vaccine reaction if she was vaccinated at that spot.
Any reaction resulting in a tumour (not the same as cancer!!!) should be looked at and diagnosed.


Keljin had a very small lump when he got his microchip as well, but it went away on its own after 2-4 weeks. At first I thought I was just literally feeling the microchip under his skin, but then I realized after a month that I could no longer feel it so that was probably the wrong idea I had. His though felt more flat, almost like a scab but under the skin instead of on top. Marble size though sounds a bit more concerning. Let us know what you find out, hoping for nothing serious.


Staff member
I would ask the vet to try to aspirate tissue from the lump and look at it under a microscope - if it's too dense to do that then I would think a biopsy would be in order.
*sigh* Ugh yeah I'm not sure where they vaccinated her for sure but the lump is right behind her left armpit. I don't know why a microchip would go there instead of between the shoulder blades but that's what the doctor guessed. I wasn't impressed with how nonchalant he was about her lump. She put up quite a fuss when she went in to be spayed, my guess is he wasn't really looking forward to fighting her again this soon after her spay. :eek: He insists we wait a few weeks but this morning she woke up with a slight limp maybe because of messing with it so much? either way I think I should call him back or find another vet... again. :(


Savannah Super Cat
I would ask the vet to try to aspirate tissue from the lump and look at it under a microscope - if it's too dense to do that then I would think a biopsy would be in order.
My vet does not like to aspirate a possible lump from a potential injection tumor. She said it better just to excise the whole thing because they are so highly malignant if it is the cancer- messing with it can cause more issues.

The good news that if it is, it can be removed if taken out quickly and completely.

I would just want to know if it was actually the chip or something else ASAP.