Characterization of breast carcinomas by two monoclonal antibodies distinguishing myoepithelial from luminal epithelial cells.

Two monoclonal antibodies, KA 1 and KA 4, raised against human epidermis, were biochemically and immunologically characterized and were shown to react with specific cytokeratin polypeptides. On frozen sections of human mammary gland, these antibodies distinguish between myoepithelial and luminal epithelial cells. We present evidence that in these cells KA 1 antibody recognized cytokeratin 5 and KA 4 antibody cytokeratin 19. In normal mammary tissue, KA 4 antibody invariably reacted with the epithelial cells lining the lumina of acini, ductules, ducts, and sinus. In contrast, KA 1 antibody decorated only the myoepithelial and basal epithelial cells of acini, ducts, and sinus. In ductules, however, KA 1 also stained the luminal cells. All 73 invasive lobular and ductal carcinomas studied reacted with KA 4 antibody; five of these were also positive, apparently in the same tumor cells, with KA 1. The tumor cells of in situ carcinomas were also stained in a homogeneous pattern with KA 4 antibody; KA 1 antibody reacted only with the surrounding myoepithelium. In epithelial hyperplasias, the proliferating cells were decorated by KA 1 and KA 4 antibodies in a heterogeneous pattern. Other antibodies were used for comparison. The results are discussed with respect to epithelial differentiation and pathogenesis and to the application of such antibodies for immunohistodiagnosis of mammary lesions.