A nevus that has grown 0.4mm in size after three years from its absence may be a manifestation of benign lesions, which are usually not dangerous at this time, but it is also necessary to be vigilant against the occurrence of cancerous lesions at a later stage. Nevus belongs to the low differentiation change of skin tissue, some nevus may gradually grow bigger over a period of time, and may become 0.4mm bigger after three years, the patient may not have obvious discomfort symptoms, and the nevus will remain stable for a long period of time. Some nevus tissues may have a higher degree of malignancy, and may also become 0.4mm larger after three years, and pathological changes such as ulceration, erosion or redness may occur locally. If a nevus becomes 0.4mm larger after three years, it is necessary to go to the dermatology department in time for medical examination, and pathological biopsy can be performed. If malignant lesions are found, liquid nitrogen cryoexcision treatment is needed to remove localized diseased tissues in time in order to have a better prognosis situation.