CD138 (Cluster of Differentiation 138) is a transmembrane heparan sulfate proteoglycan and is a member of the syndecan proteoglycan family, which mediate cell binding, cell signaling and cytoskeletal organization. The syndecan-1 protein participates in cell proliferation, cell migration and cell-matrix interactions. This antibody is a useful marker for labeling normal and neoplastic plasma cells, plasmacytoid lymphomas and various forms of Hodgkin’s disease.