The symptoms of malignant nevi are mainly the changes in the size, color and accompanying symptoms of the nevus, which are different from those of benign nevi. Malignant moles generally grow rapidly, often within a short period of time, and the color of the mole may change, from black or red or other colors for a long time to lighter, darker or uneven colors within a short period of time. Benign moles usually do not have symptoms of itching or pain, nor do they break or bleed, while malignant moles may have itching and pain, or even break or bleed without obvious triggers. In addition, malignant moles may develop local metastases in the short term, such as painless lumps around the moles or even metastatic melanoma in distant organs. In short, if a previously stable mole on the surface of the body suddenly grows rapidly within a short period of time, changes color or even shows symptoms such as itching, pain or ulceration or bleeding, we should be alert to the possibility of malignant transformation of the mole. If there is a local lump, it supports the diagnosis of malignant mole, and you should go to the hospital immediately.