Immunocytochemical identification of cell types in benign and malignant breast diseases: variations in cell markers accompany the malignant state.

We performed immunocytochemical staining of benign, in situ, and malignant breast disease to identify antigens related to the presence of the major parenchymal cell types of the normal breast. Markers for the epithelial cells, antiserum to epithelial membrane antigen, and three monoclonal antibodies (MAb) to milk-fat globule membranes stained most of the inner cells in benign breast lesions, carcinoma in situ, and invasive carcinomas, but the peripheral cells in benign lesions, as well as in carcinoma in situ, were unstained. MAb to epithelium-specific keratin 18 stained the majority of inner cells in benign breast lesions but comparatively fewer such cells in carcinoma in situ and invasive carcinoma. Markers for the myoepithelial cells, antisera, and MAb to smooth muscle actin and vimentin stained most of the peripheral cells in benign breast lesions and in carcinoma in situ but failed to stain virtually any neoplastic cells in invasive carcinomas. Markers for the basement membrane adjacent to the myoepi...