My hamsters health

Question
My daughter's hamster just turned one year old in Oct., 2006.  She's a female and her name is Lizzie.  We just noticed yesterday when we took Lizzie out of her cage that she has a lump under her right front shoulder.  At first I thought maybe it was food, but the lump is too low for it to be food (I think).  Her activity has also been decreasing in the past few days.  We normally hear her at night running in her wheel, but she has stopped using the wheel inside her cage.  When we took her out yesterday to run in her ball she kind of stayed in one place and seemed to be panting a bit.  She is still eating and drinking and when we actually handle her, she seems alert.  What do you think this lump could be?  Could it be something serious or something we should just watch?  Thanks in advance for your time and replies.

Answer
Her activity decreasing is normal with age, but the lump could be a sign of a tumor. Is the lump on both sides and is it hard or soft? I really think it's possible that it could be a tumor. You could take your hamster to a vet, but with your hamster being at an old age I would personally say just watch it and let her live her life to the fullest. The only option I know of for tumors is through surgery and there's no guarantee that your will awaken after because she's so old.