[Immunohistochemical tumor diagnosis in breast cancer--use for assessing the stage and biology of so-called "small breast cancer"].

Immunohistochemical methods assure the discrimination between neoplastic and reactive Lesions. Epithelial and mesenchymal neoplastic processes can absolutely be distinguished by antibodies directed to intermediate filaments. Growth activity of breast cancer can be evaluated using antibodies against epidermal growth factor receptor and Ki-67 proliferative protein. With antibodies directed to nuclear steroid receptor proteins semiquantitative determinations (immunoreactive score = IRS) and evaluation of genotypic heterogeneity are possible and may be helpful for therapeutic decisions.