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 myoepithelial cells, antiserum, and MAb to laminin and Type IV collagen delineated an intact basement membrane around benign lesions and carcinoma in situ, and fragmented structures in 5-10% of invasive carcinomas; the remaining carcinomas were largely unstained. Markers for both myoepithelial and epithelial cells, keratin MAb PKK2 and LP34, stained most of the inner cells in benign lesions but usually only relatively few malignant cells in carcinoma in situ and invasive carcinomas. Markers for the secretory alveolar cell, MAb to beta- and kappa-casein, stained a few isolated cells in benign lesions, many more inner cells in two such lesions in pregnant females, and none in invasive carcinomas. In conclusion, the myoepithelial cell and, under suitable hormonal conditions, the secretory alveolar cell, are retained in most benign lesions, but they are largely lost in invasive carcinomas.