Unusual inclusions in plasmacytoid cells. Their occurrence in a patient with Waldenström's macroglobulinemia.

The bone marrow from a patient with Waldenström's macroglobulinemia was studied, and histologic, immunopathologic, and ultrastructural features correlated. The infiltrating plasmacytoid lymphocytes contained PAS-negative cytoplasmic inclusions, which were shown to contain a specific immunoglobulin that matched the patients's circulating paraprotein. Electron microscopic studies revealed abundant dense fibrillar and globular material within dilated cisternae of rough endoplasmic reticulum. This material was morphologically similar to, but quantitatively different from, an endoplasmic reticulum-associated structure previously described in several patients with chronic lymphocytic leukemia. The differences between these fibrillar inclusions and Russell bodies are stressed.