FNA (fine needle aspirate) is a whole different ball game than a biopsy. They give us a clue as to what is causing the problem, how serious and how aggressive we need to get with treatment (surgery vs. watch). They are usually NOT read by a pathologist but by the vet in the hospital.
Being as they didn't find anything in need of aggressive treatment and it is at the site of a previous vaccination, this is probably a vaccination reaction. This is the most common type of vaccination reaction and in dogs and does not really require a change in vaccine used or protocol (other than going every 3 years) as long as it's a single event, IMO. This means that the body responded to the vaccination (it's supposed to), but if other reactions happen or this recurs, then a change is warranted. They often take weeks to months to resolve.
Different circumstances if this was a cat.
Doug, DVM
