The MUC-1 family of mucin glycoproteins (CA 15.3, BR 27.29, MCA, CA 549), carcinoembryonic antigen (CEA), oncoproteins (HER2/c-erbB-2), and cytokeratin (e.g., tissue peptide antigen and tissue peptide-specific antigen), among other serum indicators, have been described for BC. Here, ERBB2 is linked to breast cancer.