My 16.5 year old boy has been a messy eater for some years now as he has lost a lot of teeth over the years. He has been struggling even more over the last couple of weeks and is really only managing pate type food. Today I notice what looks like a ulcer on his lower lip,I will get him to the vet this week of course. I had a cat when I was a child who had a mouth cancerand I am fearing the worst. Is there anything less bad that this ulcer might be?