Myelin basic protein and P₂ protein are not immunohistochemical markers for Schwann cell neoplasms. A comparative study using antisera to S-100, P₂, and myelin basic proteins

Immunohistochemical localization of tissue specific or cell-specific antigenic markers in neoplastic cells has become an increasingly important tool in the pathologic diagnosis of tumors. The myelin-specific proteins of peripheral nervous system myelin, because they are normally synthesized in Schwann cells, are potentially useful markers for neoplasms arising from peripheral nerves. The authors carried out immunohistochemical studies on 18 cases of Schwann cell neoplasms, including schwannomas, neurofibromas, and granular cell tumors, to determine whether two myelin-specific proteins, myelin basic protein and P₂ protein, were present in neoplastic Schwann cells. None of these tumors showed immunostaining for either myelin basic protein or P₂ protein in neoplastic cells. In contrast, S-100 protein, which is a well established marker for normal and neoplastic Schwann cells, was localized by immunohistochemistry to neoplastic cells in all 18 neoplasms. Therefore, although myelin basic protein and P₂ protein are known to be Schwann-cell-specific proteins, they do not appear to be expressed commonly in neoplastic Schwann cells.