There are some similarities between mouth ulcers and oral cancer, but there are more differences. For oral ulcers, most of the clinical manifestations are yellow depressions in the middle covered with pseudomembranes, surrounded by obvious redness and swelling, and accompanied by severe pain. The typical characteristic of oral ulcers is that they are self-limiting, that is, they will heal naturally in 1-2 weeks. Oral cancer is also sometimes ulcerative, but most of the time it is exogenous with obvious hardness around it, and the pain may not be very obvious, but it lasts for a very long time. If clinically the patient is not sure, but the oral ulcer does not heal at all within 1 month, or even has a tendency to gradually increase in size, it is necessary to go to a professional stomatology department for examination.