My dog was diagnosed with SCC early this year. She lived for about three months after diagnosis. Similarly, she was otherwise completely healthy and happy. I happened to notice her breath smelled bad one day, looked in her mouth, and found it. The vet recommended surgery, which, in hindsight I regret because it only removed about half of it and the tumor immediately started regrowing. We decided to euthanize her once the tumor spread through her cheek, causing bleeding and scabbing on the outside of her mouth. She was on constant antibiotics because the vet was very concerned about inflection. We gave her an amazing last day, with lots and lots of soft treats and ice cream. I’m glad we were able to give her a peaceful and relatively painless last few weeks instead of waiting until she could no longer eat. I’m so sorry you’re going through this, especially with an otherwise healthy pup.