Extracellular paraprotein globules in a patient with monoclonal gammopathy

A patient with a plasma cell disorder and IgA lambda paraprotein had the unusual finding of numerous, large, opaque, extracellular globules in her bone marrow and liver. While plasma cell intracellular inclusions are well documented, identification of such material in extracellular sites is not. These globules were of various sizes, stained light to dark blue with Wright's stain, were gray in hematoxylin-eosin preparations, and were fluorescent when stained with conjugated antibodies to lambda, but not to kappa, light chains. They strongly resembled the inclusions (Russell bodies) seen in plasma cells and are believed to be massive accumulations of immunoglobulin. The clinical significance of this morphological finding is unknown, but physicians interpreting bone marrow specimens should be aware of this unusual feature.