Figure 1. Bone marrow biopsy. Sections show a small core of hematopoietic marrow showing low-normal/decreased cellularity. There is evidence of trilineage hematopoiesis. Immunostatins show the presence of patchy mild CD20 positive and small B lymphoid infiltrate (approximately 20% overall), associated with mild increase in CD138 positive plasma cells (about 5%, with formation of focal small aggregates). Overall picture is consistent with Waldenstrom’s macroglobulinemia.