Selective loss of lymphoid component simulating myeloma in lymphoplasmacytic lymphoma treated with rituximab

摘要

Loss of CD20 expression by selection pressure following rituximab therapy is recognized in B-cell lymphomas. Lymphoplasmacytic lymphoma typically shows a biphasic pattern comprising CD20-positive small lymphocytes, often lymphoplasmacytoid, together with a plasmacytic component. A 53-year-old man presented with symptoms of anaemia, and was found to have an IgM kappa paraprotein of 43 g/1. Bone marrow biopsy at presentation showed efface-ment by lymphoma, with a predominance of mature lymphocytes, including lymphoplasmacytoid forms, together with scattered plasma cells (top). The lymphoid component expressed CD20 (top, inset) and CD79a, but only the latter was expressed by the plasma cells. Within a few weeks he developed diffuse large B-cell lymphoma in a lymph node, which was treated with three cycles of R-CHOP chemotherapy (rituximab, cyclophosphamide, doxorubicin, vincristine, prednisolone) with curative intent.