Well, no obvious illness, and all of his other lymph nodes are swollen (I guess I wasn't feeling the right spots or they are not as close to the skin as I thought). They took aspirate from some of the nodes for testing. Something tells me this will be lymphoma.
We hope to have the full results tomorrow.
On the assumption that that is what it will turn out to be, my wife and I have to figure out how we are going to handle this (chemo vs. supportive therapy), and what we are going to tell our girls (aged 6 and almost 4). Either way, it will be hard to hide taking him to the vet every week.
Tomorrow (the 4th) is Skittles' 7th birthday.