S-100

S100 belongs to the family of calcium binding proteins and S100A and S100B are two members of the S100 family. S100A is composed of an alpha and beta chain whereas S100B is composed of two beta chains. This antibody stains with S-100 protein. S-100 protein has been found in normal melanocytes, Langerhans cells, histiocytes, chondrocytes, lipocytes, skeletal and cardiac muscle, Schwann cells, epithelial and myoepithelial cells of the breast,salivary and sweat glands, as well as glial cells. A large number of welldifferentiated tumors of salivary gland, adipose and cartilaginous tissue, and Schwann cell-derived tumors express S-100 protein. Almost all malignant melanomas and cases of histiocytosis X are positive for S-100 protein. S100 is of great value in the identification of several neoplasms, particularly melanomas and their metastases.