The symptoms of malignant acne are as follows: 1, localized pain, and the pain is not caused by infection or inflammation of soft tissues, usually there is no skin flushing, elevated skin temperature, etc., and the pain will be more severe at night. 2, localized acne grows faster, and it may grow very fast between 1-2 weeks or 1 month. 3, localized acne is hard and the boundary is not clear when pressed. 4, the activity is not high and the boundary is not clear. The texture of the tumor is hard, and the border is not clear, and the adhesion with the surrounding soft tissues is relatively tight, and the pain is very intense when pressing. 4, the activity is not high, and the border is not clear. If the above conditions are met, the possibility of malignant transformation of this tumor is highly suspected.