S100

The S100 family of proteins are calcium binding proteins found in many cells and involved in the regulation of a variety of cellular processes including cell differentiation, cell growth, cell cycle progression, cell motility, and cell apoptosis. S100 is expressed in melanomas, schwannomas, neurofibromas, malignant peripheral nerve sheath tumors, paraganglioma stromal cells, histiocytoma, and clear cell sarcomas. S100 is present in cells derived from the neural crest (Schwann cells, and melanocytes), chondrocytes, adipocytes, myoepithelial cells, macrophages, Langerhans cells, dendritic cells, and keratinocytes.