Mouth ulcers may be cancerous. When mouth ulcers do not heal for a long time and are accompanied by symptoms such as abnormalities in the form or function of oral tissues, it suggests that cancer may occur as follows. Under normal circumstances, mouth ulcers are self-limiting and can be healed in 1~2 weeks. If the mouth ulcers have not healed for more than 2~4 weeks, and at the same time, there is a swelling in the mouth, which grows fast and is accompanied by pain, bleeding, numbness and other symptoms, or there is a dysfunction in the oral cavity, such as restriction of mouth opening, restriction of tongue movement, etc., then it is possible that cancer may have occurred. If the above symptoms occur, it is recommended to go to a regular medical institution in time, clarify the cause of the disease with the help of doctors, and carry out professional targeted treatment.