swelling in guinea pig

Question
I have a female guinea pig (about 3 1/2 years old) and her breasts/mammary glands appear to be very swollen-- they are much larger than usual. I am concerned so I am taking her to the vet later this week but wanted to know if you had any ideas as to what might cause this in the meantime. She is definitely not pregnant. Thank you.  

Answer
Well she is on up there in age, therfore problems like tumors are a great possiblities. But don't panic, guinea pigs can get less serious problems like cysts. I am glade you are going to the vet, that unfortunatly is the only way to know for sure. Good luck and let me know how things go.