I just noticed a knot right above my 8 year old cat's left shoulder. It's small about the size of a small gum ball. Should I be worried? She acts just fine and has always been very healthy and has been an indoor cat all her life. We have one other young male cat who likes to pick fights with her sometimes, but nothing serious. Should I have a vet check it out? I just don't want to incur major fees for nothing.

