Sorry OP, that is heart breaking, especially on Christmas. I just found out today my oldest dog, about the same age as yours , has osteosarcoma on his spine, and likely only has a few weeks to live. Absolutely devastated to my core.
Worst part is my vet diagnosed him with essentially a torn ACL, so when I took him to different vet for surgery, he showed me on the xrays that my original vet had sent over, that his some of vertebrae was clearly withering away from the cancer.
How did my vet AND a certified radiologist miss this??? My untrained eyes can see it clearly on the radiographs. How did they diagnose him with a torn CCL? Incredibly frustrating, but it does not change the outcome.
Right now with anti inflammatories he is OK, but I would be lying if I said I'm not terrified of the symptoms that will manifest in the coming weeks. It may have not spread to his lungs yet, but it will. The cancer will eat at his spine until they become brittle and shatter, leaving him in agonizing pain. Just thinking about it is insufferable. This dog may as well be my first born child, and the dearest thing to me in my life. I just want to die today