Immunostains for kappa and lambda light chains are useful in distinguishing plasma cell neoplasms from reactive plasmacytosis that may be seen in connective tissue diseases, chronic liver disease, and chronic infections. In myelomas, the neoplastic plasma cells show monoclonal staining pattern (kappa or lambda) in their cytoplasm. In the example shown here, the neoplastic plasma cells are positive for kappa light chain and negative for lambda chain (see next image). In the normal bone marrow as well as in reactive plasmacytosis, the plasma cells show a polyclonal staining pattern with antibodies to kappa and lambda light chains. IHC stain. 40X. Image courtesy of: Jian-Hua Qiao, MD, FCAP, Los Angeles, CA, USA.