Hormone receptors are expressed in most breast tumor cells, and many receptors (e.g., HER2, epidermal growth factor receptor (EGFR), insulin-like growth factor-1 receptor, and platelet-derived growth factor β receptor) are present in the plasma membranes of tumor cells, which facilitates targeting because the probes do not need to enter cells. This evidence concerns the gene EGFR and breast neoplasm.