Possible Hamster Cancerous Tumour

[Golden Nugget]

Hello, guys. First off, I want to thank anyone that took the time to read this post as well as anyone who as helpful information for me. So THANK YOU! I'm new to Hamster Central as a "member," but I have been using it for references for as long as I've had him. So thanks to everyone who uses Hamster Central, you've helped me on several occasions to take care of my little Nugget baby.
To get on to the point, I believe that my hamster, a year and a half old Short-Haired Syrian by the name of Nugget, has a tumour. He had a strange growth in his cheek pouch which I thought was a piece of a cupcake mineral chew that I gave him, but I now know that that is not the case. The swollen "growth" has grown larger, as I have noticed on several occasions. Nugget has been "slowing down" recently. He is a very energetic hamster and even when I try to snuggle with him he insists on moving around and exploring. Recently he has chosen to instead cuddle up and sleep, no matter where he is. He'll wander if set down, but if he's held at all, he won't move, which isn't normal.
I am almost certain it is a tumour. He's got a bit of a bald patch in that area. If you have information to counter that claim... PLEASE TELL ME! I would love to have my concerns to rest, but if it is, in fact, a tumour. How long should I wait to put him down? (Euthanization) As much as I would like to pay for my little guy to keep on keeping on, I cannot afford the 200-300+ dollar surgeries that would be required. I'm just not sure how long I should wait. Really I don't know what to do at all. He is my first hamster, and I read up a lot on them before getting him, but I haven't had the opportunity to learn how to deal with my little guy being close to the end. Again, thanks, everyone.