Specificity: By immunohistochemistry, it specifically recognizes a protein in melanocytes and melanomas. Biochemical nature of its antigen is yet not fully characterized. This antibody reacts with junctional and blue nevus cells and variably with fetal and neonatal melanocytes. Intradermal nevi, normal adult melanocytes, and non-melanocytic cells are negative. It does not stain tumor cells of epithelial, lymphoid, glial, or mesenchymal origin.