After the discovery of Carcinoembryonic antigen (CEA, CEACAM5, and CD66e) as a tumor-associated antigen in human colon cancer [1], CEACAM5 has been found over-expressed in a high percentage of human tumors, including 90% of gastrointestinal, colorectal and pancreatic cancers, 70% of non-small cell lung cancer cells and 50% of breast cancers [2]. This evidence concerns the gene CEACAM5 and breast cancer.