Description: This antibody is specific for S-100, which belongs to the family of calcium binding proteins. It is expressed in melanocytes, Langerhans cells, histiocytes, chondrocytes, lipocytes, skeletal and cardiac muscle, Schwann cells, epithelial and myoepithelial cells of the breast, salivary and sweat glands, and in glial cells. Neoplasms derived from these cells also express S-100 protein, albeit nonuniformly. Many well differentiated tumors of the salivary gland, adipose and cartilaginous tissue, and Schwann cell derived tumors express S-100. Almost all malignant melanomas and of histiocytosis x are positive. Demonstration of S-100 is of great value in the identification of several neoplasms, particularly melanomas.