In clinical practice, we often encounter some patients with mouth ulcers, or even some patients with occasional pain in a certain part of the mouth who come for examination and ask whether it is oral cancer. So can mouth ulcers become cancerous? First of all, we have to understand what kind of disease mouth ulcer is. Oral ulcer is the general term of oral mucosal ulcer diseases, including recurrent mouth sores, traumatic ulcers, tuberculous ulcers and cancerous ulcers, etc. 1. Recurrent mouth sores are recurrent ulcers of the oral mucosa, with the characteristics of self-healing and variable location. There are no reports of recurrent mouth sores becoming cancerous. 2. Traumatic ulcers are ulcers formed by local irritation, including hard food irritation, burns, orthodontic retainers and removable dentures, etc. Traumatic ulcers will heal quickly after local irritants are removed. For ulcers formed by the edge irritation of long-term denture wear, patients who cannot heal after removal of the denture should be alert to the possibility of cancer. 3. Tuberculous ulcers also have the characteristic of not healing easily, but tuberculous ulcers are often combined with a history of tuberculosis in other parts of the body, and the ulcers will heal after anti-tuberculosis treatment. This kind of ulcer also needs to be treated in a specialist hospital. 4, cancerous ulcers ulcer surface is often large, the edge is not neat, the sore surface like cauliflower, long-term non-healing. Patients suffering from such ulcers must seek timely medical attention. Therefore, recurring ulcers with variable location and self-healing are not cancerous, but we should be alert to ulcers that do not heal for a long time. Although we should pay attention to our own health and go to the hospital for examination in time, we should not be overly sensitive to scare ourselves, as mental tension can trigger the occurrence of ulcers instead.