Osteosarcoma diagnosis but 2 vets are not agreeing and I don't know what to do
Sorry for the length but I am beside myself with what to do. On 3/16/26 My 5 year old border collie/aussie mix was trying to dig under the goat fence for some reason(she's not a digger so not sure why).. I'm not sure how long she was doing it but she managed to rip off a section of the fence and that is some pretty thick gauge metal(basically same as a residential chain link fence so she musta been violently going at this thing for a while).. I told her to stop so she came over to me and she was limping. I've had dogs limp all the time and it usually goes away in a few days, I assumed she strained something. After a week of limping I took her to the vet(they're very well respected and have in house specialists) and she did xrays, went over them with the oncologist and head surgeon and they all agreed it is osteosarcoma in berrhght shoulder. They told my she's not a candidate for amputation. She told me my girl had maybe 2 months before the cancer spread to her whole body and kills her(2 months is the standard for untreated osteosarcoma). They gave me a bunch of meds, told me to spend as much quality time as I can with her, don't take her on walks or let her play with her sister as the leg can just break and that's a horrificly painful and often worse for the owner to have to live with. They recommended euthanasia within the next few weeks and sent me home with a list of mobile euthanasia places. I obviously wanted a second opinion. I then took her to the vet that my parents use for one of my girls other sisters and I had them do imaging and opted for a fine needle aspiration which actually turned into a bone biopsy. The results were inconclusive. They did get to test the muscle and blood from the procedure and no cancer, bacteria, or fungus observed but they weren't able to test the bone for some reason(bummer cause it was super pricey and a really invasive procedure). So this vet tells me she doesn't even think she has cancer and that the "mothing" in that joint may have been something she was born with or something else(but really no true diagnosis) and when I told her I was advised to euthanize her she literally said "I don't know what vet said that but that's crazy". While we were there I also had them test for blasto fungus and that came back negative. She stopped limping about a week after the procedure So, now I got differing opinions so I took her back to the original vet few weeks ago(6 weeks after the initial xrays) and she took new xrays and to her surprise the legion had not grown at all, she was in no pain while having the joint manipulated, and she had no tumors anywhere. I asked if this was such an aggressive cancer with a 2 month prognosis if she would have expected to see further damage to the original legion and also spreading to other areas to which she replied "I would have expected to see that".. But then she couldn't give me any reason why it wasn't progressing like it is "supposed to". A few days later she sends me this huge long email about how she once again went over the imaging and test results with even more of the specialists and they all agree cancer and humane euthanasia. That was 3 weeks ago. So here I am with a dog who shows zero signs of pain, no limp, no behavior change, still wants to jump up on the couch, still wants to chase rabbits etc, so I started taking her on short walks just cause it seems like torture for her to just sit inside all day and do absolutely nothing especially when she's a farm dog with high energy breed mix, and she seems totally fine. Time wise; it's been 9 weeks since she injured herself which is 1 week past when I was told she was going to be dead. I have absolutely no clue what to do. There is an obvious void in the xrays in shoulder but I'm getting 2 vets advising wildly different courses of action and all I want is the best for my girl. If I have to euthanize her I will, but I refuse to do that when I have literally zero proof she has cancer, 2 different opinions, a dog showing zero signs of discomfort, no progression of a cancer that was supposed to have already spread and killed her. What on earth am I to do? I couldn't post images for some reason so here's links to the xrays.
3/24/26 https://ibb.co/g85VgPW 5/1/26 https://ibb.co/zhSJTRsg And here's one of her just cause https://ibb.co/gFVmhMXJ