Canine bone cancer

One of my rescues is now 15. She started limping and I took her to the vet. From the xray, the vet is pretty certain it is bone cancer right below the sholder joint. The biopsy was not conclusive. The pathologist at the university suggested a more aggressive biopsy. My vet is concerned to do that might possibly break the bone.
My friend thinks I should put her down. It ain't gonna happen. The conversation got a little heated as she likes to tell people what to do and not too happy if they disagree. She is on Deramax for her arthritis and now pain medicine, my dog, not my friend! :O) She is getting around fine with just a bit of a limp. If cancer, the options are: amputate the leg with the probability of it returning, chemo and radiation with no guarantees, or just keep her comfortable for now.
I questioned if it could be some type of infection in the area to cause the shading on the xray. It is possible so she will be on antibiotics for 3 weeks and then new tests.
Has anyone dealt with canine bone cancer? Where was it located and what did you do?
As I've told my vet in the past, I didn't recue my animals to just let them die and have had some pretty high vet bills. When a rescue, you don't have a medical history, you don't know what they have been exposed to nor what they have gotten into for food. As I rescued them it is my responsibility to keep them safe. I will do whatever I need to but would appreciate your input.
Thankyou
Lynn