Demonstration with monoclonal antibodies of an unusual mononuclear cell infiltrate and loss of normal epithelial membrane antigens in human breast carcinomas.

Monoclonal antibodies to two differentiation antigens normally expressed on the membranes of breast epithelial cells were used in immunofluorescence studies on frozen sections of malignant breast tumours. It was demonstrated that most tumours did not express these antigens on their cell membranes, and it was possible to classify histologically indistinguishable tumours according to whether they expressed the antigens. The absence of these membrane antigens is likely to be a subtle indicator of cellular differentiation and to have metabolic and other functional implications for the tumour. The demonstration that otherwise indistinguishable tumours can be classified in this way therefore has obvious potential for clinical exploitation. In addition, it was demonstrated that the majority of the mononuclear cells in those tumours with intense mononuclear cell infiltrates expressed an antigen not normally found on mature lymphocytes and macrophages.