Outpatient clinic often encounter this situation, when some people body parts grow black spots, will be more nervous, come to consult whether the malignant change, here I give you on the prevention and treatment of nevus pigmentosus. 1, first of all, need dermatologist to distinguish whether the black spot of skin is pigmented nevus or not: exclude the possibility of other pigmented spots 2, secondly, after diagnosed as pigmented nevus, most of them don’t need special treatment 3, out of the following 10 kinds of cases, need dermatologic surgery for skin cosmetic surgery to excise: (1), special parts: the end of the limb, the bottom of the foot, the palms of the hands, the lips and the genitals and other easy to friction parts (2), in a short period of time Volume increase: doubled within 6 months (3) Color change: uneven pigmentation, or deepening and fading of color (4) Satellite foci around the primary rash: new pigmented nevus surrounding the primary nevus (5) Pseudopods in the primary rash: the shape of the primary nevus has become irregular, and there is a phenomenon that the nevus is rooted to the surrounding area (6) Ulceration or bleeding (7) Self-awareness of symptoms such as pain or itch (8) If the nevus has recurred after laser, freezing, or medication (9), if the nevus has serious psychological disorders (10), or if the nevus has cosmetic needs.