S100B belongs to the S100 subgroup of the EF-hand family of calcium binding proteins. It is a homodimer that is expressed primarily in the brain by astrocytes, oligodendrocytes and Schwann cells. S100B has multiple intracellular functions, but can also be secreted from cells to exert extracellular functions. Some of the extracellular functions of S100B may be mediated by RAGE (receptor for advanced glycation end products). Blood levels of S100B can be used to monitor the extent of brain injury and malignant melanoma.