What would cause an oral polyp to recur in my cat?

Question

About a year ago my then-newly-adopted adult male cat had a small growth under his tongue, which my vet removed and biopsied. It was a benign fibrous polyp, which I understand sometimes happens.

Now, almost a year later, he has another one (much smaller so far) in the same place. My vet was surprised; she said they don't usually come back like that. The surgeon who removed the first one happened to be there so we consulted her too, and she said she'd never seen that before and she believed she'd left a large enough "buffer zone" in removing the first one, but she'll leave a larger one this time.

My vet recommends removing and biopsying this one and I will follow that recommendation. My question is: what might be causing this? Should I expect it to happen yet again in the future? Is there anything I should be doing to reduce the likelihood of recurrence?

The cat is estimated to be about 5 years old, indoor-only, and eats standard dry and canned food with the occasional treat. He is missing several of his teeth (incisors); we don't know why (he came that way). I understand that sometimes polyps form around foreign bodies; this was not the case the first time. I'm not aware of any mouth injuries and he hasn't been in any fights involving biting.

Answer 1

So, assuming that a new source is not the basis (e.g. foreign object) and this is a recurrence of the polyp in the same location, then the primary cause for return is that there were still neoplastic cells outside the surgical margins (her "buffer zone") and/or the excision didn't include periodontal structures (this is from Blackwell's Consult, Canine and Feline, 5th edition).

You can also find some further reading (much older study) on Feline Oral Neoplasia, recurrence is rare with humans, but not unheard of, and that feline treatment would be similar.

Also, this odontogenic tumors article from vet dental specialist talks about possible frequency of recurrence when the surgical margins are insufficient as well.