Immunoglobulin inclusions in non-Hodgkin's lymphomas.

The occurrence and characteristics of intracellular immunoglobulin inclusions in non-Hodgkin's lymphomas are described. Lymphoma cells from three patients with immunoblastic sarcoma contained classic cytoplasmic, periodic acid-Schiff (PAS)-positive Russell bodies. Immunoperoxidase staining revealed monoclonal IgG (k) in two cases and a polyclonal pattern in the third case, where the tumor evolved from a reactive lesion. Unusual cytoplasmic inclusions were observed in the neoplastic cells of two patients with follicular center cell lymphoma. In one case large globular structures lacking a distinct limiting membrane were seen, while the cells of the other patient contained "signet-ring-like" vacuoles filled with microvesicles. Both were PAS-negative and showed monoclonal immunglobulin staining. In two other cases PAS-positive intranuclear inclusions consisting of monoclonal immunoglobulin IgM(k) could be demonstrated. The possible significance of these findings in B-lymphocyte derived neoplasms is discussed.