How to tell if a canker sore is cancerous?

If the cancer won't heal in a few days it may be cancer. your statement relative to dipping I take it as tobacco? if this is correct, stop it now. I used to smoke cigars and pipes as well as cigarettes and 30 yrs after I stopped, I had cancer of the tongue. I tell you this.........surgery of the tongue hurts more than any operation I had. Otherwise, seeing the dentist will help. Usually, they can tell. If it's suspicious, a biopsy will determine it.