S100 Immunohistochemistry Biopsy Tissue

S-100 expression is seen in cartilaginous tumors, myoepithelial tumors, Schwann cells and neural tumors, Langerhans cell proliferations, benign and malignant melanocytes, clear cell sarcoma, and some carcinomas particularly of the breast. S-100 staining occurs both in the nucleus and cytoplasm. The S100 proteins are a family of low-molecular-weight proteins found in vertebrates and characterized by two calcium-binding sites that have helix-loop-helix conformation. Several members of the S100 protein family are useful as markers for certain tumors and epidermal differentiation. It can be found in melanomas, 100% of schwannomas, 100% of neurofibromas (weaker than schwannomas), 50% of malignant peripheral nerve sheath tumors may be weak and/or focal, paraganglioma stromal cells, histiocytoma and clear cell sarcomas. Further, S100 proteins are markers for inflammatory diseases and can mediate inflammation and act as antimicrobials.