Neurocutaneous melanosis is a rare congenital disease that is characterized by the presence of giant pigmented nevus of the skin and proliferation of melanocytes producing melanin in the central nervous system. We describe a case of neurocutaneous melanosis, in which we detected cells in the cerebrospinal fluid showing abnormal Samson staining. The diagnosis was confirmed by the detection of abnormal cells that have pigment granules by cytological analysis of the cerebrospinal fluid. We were able to detect pigment granule cells not only by cytological analysis but also by Samson staining of the cerebrospinal fluid. This case shows that screening by Samson staining can provide clinically important information in terms of the diagnosis of neurocutaneous melanosis.
