Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) Neurocutaneous melanosis ?
    ### Response:
    Neurocutaneous melanosis (NCM) is a rare, non-inherited condition of the central nervous system. It is characterized by melanocytic nevi in both the skin and the brain. Two-thirds of people with NCM have giant congenital melanocytic nevi, and the remaining one-third have numerous lesions but no giant lesions.
    