Structural distinctions among human breast epithelial cells revealed by the monclonal antikeratin antibodies AE1 and AE3.

Two monoclonal antikeratin antibodies, AE1 and AE3, were used in indirect immunocytochemistry to examine keratin expression in normal, benign proliferative, and malignant human breast epithelium. Both antibodies reacted strongly with most luminal cells in ducts and acini of normal gland. While AE1 did not stain myoepithelium, AE3 recognized myoepithelial cells of ducts but not acini, implying a cytoskeletal difference between the myoepithelium of these two components. Moreover, the antibodies reacted differently with the myoepithelium of intracanalicular as compared with pericanalicular types of fibroadenomas. Tumour cells of infiltrating ductal carcinomas with a prominent intraductal component stained more homogeneously with AE1 and AE3 than those without intraductal growth. The results provide evidence for two phenotypes of myoepithelial cells and for the presence of cryptic keratin epitopes in human breast epithelial cells. The finding that neither AE1 nor AE3 is a universal detector of these cells has important clinical and experimental implications.