A number of serum carcinoma protein markers in breast cancer have been identified, including CA15-3, CA27-29, CA-125, carcinoembryonic antigen (CEA), tissue polypeptide antigen (TPA), circulating extracellular domain of human epidermal growth factor receptor 2 (HER2), and tissue polypeptide-specific antigen (TPS) [63,64]. The gene discussed is CEACAM5; the disease is breast cancer.