CD15 is a complex cluster of cell surface glycoproteins and glycolipids with a common trisaccharide structure, 3-fucosyl-N-acetyllactosamine (3-FL), also referred to as Lewis X (LeX) antigen. This antigen is involved in neutrophil functions such as, cell-cell interactions, phagocytosis, stimulation of degranulation and respiratory burst. It is present on >95% of granulocytes including neutrophils and eosinophils and to a lesser degree on monocytes. The CD15 is expressed in Reed-Sternberg cells, myeloid cells as well as epithelial cells. CD15 antibody has been used as an immunohistochemical marker to identify Reed-Sternberg cells (RSC) in classical Hodgkin lymphoma (CHL) and distinguishe it from Hodgkin-like neoplasms. CD15 does not stain mesotheliomas and is therefore most useful for distinguishing epithelial mesothelioma from adenocarcinoma.