Robyn, we had a lump removed from Cass shortly after she arrived here. The aspiration showed very suspicious cells and the vet suspected a mast cell tumor so we had it taken out. They took large margins, too, to make sure they got it all. Poor girl even had a drain for a while.
Path report came back as a vaccination reaction lump
We didn't cotton onto it right away cuz the lump didn't show up for two weeks past the vaccination... *sigh*
Anyway, the point of the story is that needle aspirations are not always accurate, and vets are fooled now and then. I'm hoping that's the case with Thorin.