Immunohistochemical studies of S-100 protein expression in myoepithelial cells of benign breast diseases and normal breast tissues.

We studied benign breast diseases using polyclonal anti S-100 protein and monoclonal anti a-subunit or beta-subunit of S-100 protein antibodies. The antibody gave positive staining in most of the cytoplasms and nuclei of the myoepithelial cells of normal breast tissues, gynecomastia, fibroadenoma, intraductal papilloma and mastopathy. However, immunohistochemical methods using the monoclonal antibodies for them did not reveal positive staining in the myoepithelial cells.