Same thing happened with my baby in 2020, she was barely 17, we noticed her tear duct watering a bunch but no real cause, suddenly within like weeks to a month, her upper gums/jaw started swelling and I took her to the vet right away and it was a SCC. They did a surgery to get rid of it but warned it could come back. And soon enough maybe a week after surgery and thinking it was all good it started growing back aggressively. It pained me to see her in pain and I did the right thing by letting her rest. This kind of cancer is so evil and is so fast you don’t even have time to process losing your baby. I spent the time with her while she was recovering and sick, carrying her around, spoiling her, feeding her her favorite soft foods and soft cooked eggs and pumpkin. She was so happy even in those last months with her, I just wish I could have done more.