Since glycosylated-proteins have been discovered to be the clinical biomarkers for many diseases, for example, Her2/neu in breast cancer, prostate-specific antigen (PSA) in prostate cancer, CA125 in ovarian cancer, and carcinoembryonic antigen (CEA) in colorectal, bladder, breast, pancreatic and lung cancers, glycoproteomics, as a significant branch of proteomics, has become an emerging field for biomarker discovery [5,6]. Here, CEACAM5 is linked to breast cancer.