Figure 3. Bone marrow involvement by lymphoplasmacytic lymphoma. (A) Bone marrow aspirate showing many neoplastic plasma cells with abundant cytoplasm mixed with mature small neoplastic lymphocytes. (B) Bone marrow biopsy showing a hypercellular marrow infiltrated by numerous lymphoplasmacytic cells in an interstitial pattern (40×). (C–F) Immunohistochemical stains: B cells highlighted by CD20 (C) and plasma cells by CD138 (D) that lack significant expression of kappa (E) or lambda (F).