Almost everyone has a “nevus” on their body. A nevus, also known as a pigmented nevus, is a common name for a variety of benign melanocytic tumors. It is not uncommon for nevi to become fatal or malignant due to improper treatment. Some people are highly nervous about it, while some people are unconcerned about it. The scientific attitude is to understand it and deal with it properly. Congenital nevi are more dangerous There are more than 20 types of nevi, and the most common ones are common acquired nevi and congenital nevi. Common congenital nevus is found in almost everyone and usually occurs in childhood, mostly at the age of 1~2, but a few new lesions can still appear until the age of 27 or 28. Most of them gradually elevate above the skin surface and become flat or hemispherical pigmented papules. The lesions are uniformly pigmented, with smooth surfaces and neat edges. Except for the face, the lesions gradually become softer, smaller and lighter in color after middle age, and even the entire lesion disappears completely. Therefore, it is rare to see nevi on the elderly. This kind of nevus is generally not easy to become malignant and can be treated without treatment except for cosmetic needs. Congenital nevi are nevi that are present at birth, with an incidence of about 1%. Small ones are a few millimeters, while large ones cover most of the body. Those larger than 20 cm are generally called congenital giant nevi. In addition to varying in size, congenital nevi often have a variety of forms, including spots, rashes, papules, plaques, nodules, papilloma-like or tipped papules. In some cases, nodules of varying sizes may appear on top of large plaques, with irregular margins, non-smooth surfaces, non-uniform pigmentation, and lesions with coarse hairs. Recently, statistics have been made on patients with cutaneous melanoma. Among them, 24 patients (13.0% of the total) had malignant changes from congenital small nevi, 3 patients had malignant changes from congenital giant nevi, 1 patient had malignant changes from acquired nevi, and 3 patients had malignant changes due to laser treatment. Our previous studies have fully proved that congenital nevi are more prone to malignant transformation than acquired nevi and should be removed. Small congenital nevi can be removed after the child is able to cooperate. The “black nevus” that is hard to distinguish from the real one is actually not equal to benign melanocytic tumor, because many black lesions on the skin can be mistakenly called “black nevus”. These include nevi, seborrheic keratosis, senile nevi, solar keratosis, basal cell carcinoma, fatal melanoma, etc. Some of them are very difficult to distinguish from “nevi” and even the most experienced dermatologists can still make mistakes. Recently, we counted 1024 cases treated with “nevus” in the Department of Dermatology of Xijing Hospital in the past 5 years, and as a result, only 870 cases matched the diagnosis of nevus in pathological examination, and as many as 154 cases did not match the diagnosis, mainly 6 cases of malignant melanoma and malignant transformation of nevus, 13 cases of basal cell carcinoma, 75 cases of seborrheic keratosis, 13 cases of epidermal cyst, and 7 cases of dermatofibroma. There were 7 cases of dermatofibrosarcoma. The Department of Dermatology of Xijing Hospital is a national key discipline and a dermatology center of the whole military, and nevus and melanoma are the focus of our research, but there are still a large number of diagnoses that do not match with the pathological results, which shows that it is difficult to distinguish the true from the false “nevus” and difficult to diagnose. Because of this, no matter whether it is a real nevus or not, we should pay attention to it, wait and see what happens, and receive diagnosis and treatment if necessary. Recommended surgery for moles The malignancy rate of moles is actually very low, so there is generally no need to worry too much. If treatment is needed, surgical excision and pathological examination should be performed, and treatments such as freezing, laser and drug erosion should not be done. The reasons are: ① surgical excision is quick to recover, does not leave scars and has good cosmetic effect, while laser and freezing damage the surrounding normal skin, slow to recover and often leave scars. ②Treatment such as freezing, laser and drug erosion are often incomplete, and the mole cells that have not been removed may become malignant due to stimulation. ③Pathological examination can be done after surgical excision to make a clear diagnosis, and if problems are found, they can be remedied in time, while freezing, laser and drug erosion cannot achieve this purpose. ④Early melanoma (malignant) looks like a “nevus” to the naked eye, and pathological examination can be performed after surgical excision to make a clear diagnosis and take remedial measures. Some nevi such as nevus of Ota (greenish-brown spots around the eyes) and nevus of Ito are almost non-malignant, and modern Q-switched laser can cure them completely without damaging normal skin, which is one of the most important advances of modern laser medicine. In addition, some black spots of 2~3mm in size are commonly seen on the face and various parts of the body, which are also called “nevi”, and the correct name is nevus, and such black spots can be completely removed by laser and drug erosion without any concern. Prevention of malignant melanoma The proliferation of melanocytes in the skin to form a benign tumor is a nevus; however, if it forms a malignant proliferation, it is a fatal melanoma. How to prevent melanoma? First, pay attention to your “nevi”, especially congenital nevi. If a nevus increases significantly after puberty or a raised papule appears on a flat black spot, or if a nevus is painful and uncomfortable, or if the pigmentation deepens significantly, or if a red halo appears around the nevus, it may be a sign of a malignant nevus. Next, pay attention to the nail black line. The nail black line is called nail mother nevus. We have 46 cases of melanoma occurring under the nail, among which 9 cases started as nail black line and after several years the black line widened to form melanoma. Thirdly, pay attention to the new black spots, especially the black spots on the soles of the feet. Black spots on the bottom of the foot are not painful and harmless, but in fact they are often the most dangerous “terrorists”. In addition, new moles rarely appear after the age of 30 (many “moles” are actually seborrheic keratoses, commonly known as age warts). However, if a new “nevus” occurs and is more than 0.5 cm in size, special attention should be paid and it is important to go to a major hospital to see an experienced dermatologist for a diagnosis to rule out melanoma. In short, with vigilance, malignant melanoma of the skin can be nipped in the bud and not lead to serious consequences.