If a single ulcer lasts for more than a month and the symptoms are gradually aggravated and not alleviated, it is recommended that the patient should seek medical attention in time and go to a professional stomatology department to have a pathological biopsy of the ulcer, that is, to cut a small piece of biopsy tissue around the ulcer and send it to the pathology department for laboratory tests to check whether the ulcerative lesion has become cancerous. This is a clinical situation that requires vigilance, but it should also be noted that recurrent ulcers, which are common in clinical practice, are not cancerous, so there is no need to worry about them and they should be treated symptomatically. The typical symptoms of recurrent ulcers, also known as oral aphthous ulcers, are redness and swelling around them, sometimes with a yellow depression in the middle, and severe pain. This type of ulcer is characterized by self-limiting and recurrent, which means that it will heal naturally in about 1 to 2 weeks, but will reappear in the original area or other areas after a while. We need to be alert to the ulcer that lasts for more than one month in a single part as mentioned before. This kind of ulcer is clinically different from the common aphthous ulcer, most of them are cauliflower-shaped or rat-like, and the texture is relatively hard.