Proteins in use as tumor markers include oncofetal proteins such as alpha-fetoprotein (AFP) and carcinoembryonic antigen (CEA); protein fragments such as tissue polypeptide antigen and cytokeratin-19 fragment antigen 21-1 (CYFRA 21-1); and various immunoglobulins including Bence Jones proteins, as well as other proteins such as β2-microglobulin, chromogranin A, human epididymis protein 4 (HE4), thyroglobulin, squamous cell carcinoma antigen (SCC), and S100 protein (Figure 1A) [24]. Here, CEACAM5 is linked to neoplasm.