my new old rat

Question
I just adopted a rat from petco about a week ago.  It seems she is a lot older than I thought she was, I just noticed that she has developed bumblefoot on both rear legs and she has a small tumor on her side,she was very active when i got her but she has gone downhill very fast.  Should i take her to the vet to get her feet treated or would this just cause unneeded stress on her since she is so old?

Answer
I would definitely get her feet treated.  Even though she may be old, she could only be acting decrepit because she is in a lot of pain.  Bumblefoot is quite painful, as the rat's feet become very infected and sore and they have no choice but to continue to walk on them.  If her cage has any wire levels or ladders I would suggest removing them until she is healed, and if possible switch her bedding to something comfortable to walk on (ie not compressed paper pellets) while she heals.

Having the tumor removed is a decision you and your vet will have to make.  Most tumors can be easily removed, though they do often come back.  Since she is otherwise ill, I wouldn't bother having the tumor taken care of until her feet are healed or mostly healed.  No need causing her too much stress with a surgery on top of daily antibacterial scrubs and antibiotics.  After her feet are healed it probably would be a good idea to have the tumor removed, provided she is acting healthy and normal after her feet treatment.

Hope everything turns out well, let me know what happens!