As B-cell development progresses towards plasma cells,CD138, also known as Syndecan 1, is expressed. It can beutilised to distinguish between marginal zone lymphomaand lymphoplasmacytic lymphoma. 1 ALK+ large B-celllyphoma (LBCL) typically exhibits high expression of CD138,but ALK+LBCL is not stained by lineage-associated markersincluding anti-CD20 and anti-CD79a. HHV8-associatedprimary effusion lymphoma exhibits immunoreactivity toanti-CD138 despite the absence of B-cell markerexpression in the lymphoma cells. In bone marrow biopsyspecimens, anti-CD138 is a useful marker for identifyingand counting plasma cells, whether they are reactive,benign, or malignant. Epithelial cells also express CD138.