What could these lumps indicate?

I noticed a few dime-sized lumps on my dog’s back, about two months ago. They feel kind of soft, and movable to a degree. My first instinct was cancer and to take her to the vet right away, but on the advice of a friend I decided to wait and see if they went away or if I noticed other symptoms. One of the lumps disappeared, but the other two did not change. My dog is an 11 month old chihuahua so I would think cancer would be very rare, no? They still are not hurting her. I haven’t noticed anything weird (other than the lumps)... she is eating normally, no weight loss, she’s playful as ever. I’m wondering if they are just fat deposits. Basically I am worried about taking her to the vet and having all the tests they want done, which include biopsies and blood work (which get expensive), and having it turn out to be nothing. I have the money if need be, but I am a student and I don’t want to just throw it away. I know my dog’s health is important and I love her to death… I’m just wondering if anyone has been in a similar situation with their dog or if anyone could offer some ideas as to what we may be dealing with.