To demonstrate the potential of the mAb785–epitope system for breast cancer targeting, representative breast cancer cells from four different genotypes were selected, including ZR75.1 (luminal A subtype), MCF-7 (luminal B subtype), SKBR3 (Erb-B2 overexpression subtype), and MDA-MB-231 (basal-like subtype). This evidence concerns the gene ERBB2 and breast cancer.