I remember when we took the last trip to our vet's for our other dogs-- I always swore I was never getting another dog . After a few months the longing started and I would start looking for another. Right now we're down to one little one and she's 12. I know she has a few years yet but I also know that anything can happen without warning when they reach that stage. Very fortunate that she is still as healthy as the day I picked her up and I hope things will remain that way. I also know I should be looking for another dog so that I'm not left without one if and when she does have to go but now I'm wondering if she would feel slighted.
That lump could be just a fatty tumor, they're harmless and most old dogs get them. Stay happy and bouncy for your dog's sake, they feel our every mood. It would be sad if she were to sense the vibes and become depressed.