An abcess was never mentioned - I think a few weeks later it was obvious from the shape of the poor animal's head that it was a large tumour - Fudge, the hamster was not much older than yours, certainly not a year old.
However, over the years, that is the only one that has been so poorly so early on in life - I've had quite a few hamsters over the last 25 years or so, and many have lived to see their second birthday!
May I ask if your hamster's behaviour changed as a result of the tumour? Our dwarf seems to be more or less her normal self, although slightly more jumpy, and maybe using her wheel a little less. A week of antibiotics later, things don't seem to be improving.
One thing struck me this week when I read something online. We had an insect repellent thingy (one that emits a high-pitched noise inaudible to humans) plugged in within two feet of her cage. I didn't even think of it as a possible problem before, but I have now moved it to another room. She has never acted as though it has caused her stress, but I wonder now whether it did, and whether this may have resulted in bodily symptoms.