Biomarkers such as carcinoembryonic antigen (CEA), vascular endothelial growth factor (VEGF165), MUC1, platelet-derived growth factor (PDGF), and human epidermal growth factor receptor 2, play a critical role in the diagnosis of breast cancer in the early stages (Table 1) [22,33,48,49,50,51,53,54,55,57,58,59,60,61,62,63,64,65,73,74,75,105,106,122]. The gene discussed is CEACAM5; the disease is breast cancer.