Welcome to OCF, Jan! Im so very sorry you're concerned about your mouth. Hopefully what you have going on is nothing serious and its easily fixed. There are so many different things it could be besides cancer!!! Many adults will have an occasional mouth sore once in a while during their lifetime. Most are nothing serious but occasionally someone will have a mouth sore thats been there for over 2 or 3 weeks and it has not resolved itself. At that point its time to get the sore checked by a professional. The best professional to check the spot would be an ENT (ear, nose and throat doc) who specializes in treating oral cancer patients. I suggest seeking out an ENT to check your mouth and take a good look at your mouth sore. Id advise you to still keep your dental appointment but also make an ENT appointment. Unfortunately many dentists arent familiar with oral cancer and do not offer oral cancer screenings to their patients as their focus is only on their patients teeth. Im wishing you all the very best with this. Please keep us posted on how you make out. Good luck!!!