However, even before the era of precision medicine, many proteins produced in elevated quantities by tumor cells, such as Bence-Jones protein, beta human chorionic gonadotrophin (β-HCG), alpha-fetoprotein (AFP), carcinoembryonic antigen (CEA), prostatic acid phosphatase, and human epidermal growth factor receptor (EGFR), and EGFR-2 (HER2), were used as circulating biomarkers of disease activity aiding in immunodiagnosis [4] or even as targets for radionuclide- or drug-conjugated antibodies [5, 6]. The gene discussed is CEACAM5; the disease is neoplasm.