Heterogenous expression of the EGF-receptor in human breast carcinoma

The epidermal growth factor receptor was analyzed in the membrane fraction from a series of human breast carcinomas using a radioligand assay. The results were compared to immunostaining with monoclonal antibodies on tissue sections. All tumors with detectable receptor levels as measured by ligand binding showed a positive staining with monoclonal antibodies. In such tumors more than 50 percent of the cells were receptor positive with varying intensity. Tumors classified as receptor negative with the radioligand assay could be divided into two major groups based on their immunostaining. The largest group showed no reactivity with monoclonal antibodies. In a second smaller group a positivity was observed in small clusters of tumor cells while the majority of cells were negative. The staining intensity in such clusters was usually low. It seems possible that this heterogenous expression of the epidermal growth factor receptor is of significance with respect to clonal selection in tumor spreading.