If the mole at the corner of the mouth is a benign lesion, it can be left alone for now, and if it has a tendency to become malignant, it should be removed. Nevus, also known as nevus cell nevus, is caused by melanocyte aggregation and proliferation in the local area, it is a benign tumor, the disease progresses slowly, usually there is no self-conscious symptom, no need for treatment, if it affects the aesthetics, the local area can be taken as a laser treatment to remove the nevus cell nevus. If it affects aesthetics, localized laser treatment can be adopted to remove nevus cell nevus. If it is rubbed for a long time or exposed to ultraviolet rays, nevus cell nevus is prone to malignant transformation, and it needs to be surgically excised promptly. Usually when nevus cell nevus undergoes malignant transformation, it manifests itself as uneven color of nevus, irregular boundary, gradual enlargement of boundary, mucous membrane rupture and bleeding, local itching, local pain, and enlarged lymph nodes near the pigmented nevus and other symptoms. It is recommended that patients should go to regular hospitals in time if there is any symptom of malignant transformation according to their own situation, and receive reasonable treatment under the guidance of professional physicians.