CD15, also known as Lewis X or SSEA-1, is a fucosylated carbohydrate antigen found on the surface of various cells. It is a complex cluster of cell surface glycoproteins and glycolipids with a common terminal pentasaccharide. CD15 plays a significant role in cell adhesion and migration, particularly in immune responses and development. It is expressed on most terminally differentiated myeloid cells, including granulocytes, eosinophils, and monocytes/macrophages, but not on hematopoietic progenitor cells. In addition, CD15 is found in various epithelia and neural tissues. In cancer, CD15 is present on the membrane proteins of several types of cancer cells, such as renal, prostate, and breast cancer cells. It interacts with selectins to facilitate cancer cell adhesion to endothelial cells, promoting metastasis. Therefore, CD15 has potential as a therapeutic target and prognostic marker in cancer treatment.