CEACAM5 and breast cancer: Copious studies on the "classical" biomarker, namely, CEA, showed involvement in the immune response, cellular contact, cell adhesion, anoikis resistance, and liver metastasis promotion [10]. Determination of serum levels of circulating CEA by enzyme-linked immunosorbent assay (ELISA) tests has assisted in assessing colorectal, lung, gastric, pancreatic, and breast cancer progression.