Giant nevi may cause a lot of troubles for children, including itching and recurrent ulcers, cosmetic deformities and dysfunction, and psychological disorders caused by the abnormal appearance; perhaps the greatest concern for parents is the possibility that the nevus may transform into a malignant melanocytoma. In addition, many parents may not be aware that giant nevi may be associated with other systemic diseases, such as scoliosis and spinal canal closure insufficiency. Most parents of malignant melanocytoma may be concerned that the site of malignancy is located within the cutaneous nevus, but malignancy can also occur in tissues other than the skin, such as the mucosa of the gastrointestinal tract, the central nervous system, and the retroperitoneum. The incidence of malignancy in congenital giant nevi was previously reported to be high, ranging from 1.8% to 45%. However, recent reports indicate that the incidence of malignancy in giant nevi is actually much lower than previously reported values, ranging from 0.9-2.8%, but even so, the incidence of malignancy in giant nevi is 0.6% higher than in the normal population. Risk factors for malignant transformation: 1. moles appearing in more than one part, especially in more than three parts; 2. the larger the area of giant nevus, the more likely it is to become malignant; 3. giant nevus with satellite nevus is likely to become malignant; 4. giant nevus located in the trunk area is likely to become malignant. Time of malignant change: 50% of malignant changes occur within the first three years of life, 10% occur in childhood, and 10% occur in adolescence. Therefore, 70% of malignant changes occur before the age of 13. Manifestations of malignant transformation: accelerated local growth of nevus, ulceration and bleeding of nevus, itching or painful symptoms of nevus, deepening of nevus color and increase of satellite nevus. Neurocutaneous melanosis Neurocutaneous melanosis is a disease in which melanocyte proliferation occurs in the central nervous system of patients with giant nevi. This abnormal proliferation of melanocytes can be benign or malignant, but even in the absence of malignancy, it can exhibit severe symptoms such as hydrocephalus, epilepsy, mental retardation, cranial nerve palsy and spinal cord tethering. Neurocutaneous melanosis has two periods of prominent symptoms: 1) in infancy, when children have increased cranial pressure, hydrocephalus and mental retardation; 2) between the ages of 20 and 30, when patients develop intracranial occupying lesions, increased intracranial pressure and spinal cord compression symptoms. The risk factors for neurocutaneous melanosis are: 1) a high number of satellite nevi (>20); 2) giant nevi located in the midline. Children with these risk factors should be screened for the disease at 4-6 months of age with an MRI of the central nervous system.