A pigmented mole is a very common benign skin swelling that generally has no effect on human health. However, nevus can become malignant and can be confused with many other skin diseases, so it is important to know about nevus. From the point of view of organization, pigmented nevi can be divided into junctional nevi, mixed nevi and intradermal nevi. Junctional nevi are usually flat on the skin surface, while mixed nevi can be slightly elevated on the skin surface, and junctional nevi and mixed nevi can become malignant; while intradermal nevi are mostly hemispherical elevations or nodules with tips, which can have hair growth and are less likely to become malignant. In terms of time of occurrence, pigmented nevi can be divided into congenital and acquired pigmented nevi. Congenital pigmented nevi occur at birth or shortly after birth, and those with large area and hair growth are called animal skin nevi. Congenital pigmented nevus can become malignant and active treatment is recommended. Acquired pigmented nevi are pigmented nevi that occur in adults, most of which are benign, but special attention should be paid to pigmented nevi in friction areas such as hands and feet. Doctors suggest the following: 1. congenital pigmented nevus with diameter greater than 0.5 cm; 2. pigmented nevus on hands and feet and friction-prone areas [belt and bra tightly bound areas]; pigmented nevus with frequent rubbing on scalp or jaw area; 3. nevus rapidly increasing in size or nodules appearing below it; 4. color rapidly deepening, darkening or redness around it; 5. frequent bleeding, scabs on surface or ulcers occurring 6.A black satellite spot appears nearby; 7.Pain, itching or burning sensation occurs locally; 8.Enlargement of adjacent lymph nodes; 9.Pigmented nevus on the exposed part of the face affects the aesthetic appearance Once one of the above manifestations occurs, it is recommended to remove it surgically and send it to pathological examination for clear diagnosis.