Diffuse large B-cell lymphoma with distinctive patterns of splenic and bone marrow involvement: clinicopathologic features of two cases.

Two unusual cases of large B-cell lymphoma with predominant splenic and bone marrow (BM) involvement and similar clinical and histopathologic features are described. Both patients presented with nonspecific constitutional symptoms, unexplained cytopenias, and splenomegaly. Splenectomy revealed diffuse red pulp involvement by large B-cell lymphoma. The perisplenic lymph nodes were also involved diffusely with effacement of normal nodal architecture, excluding a diagnosis of intravascular large B-cell lymphoma. BM biopsies revealed striking erythroid hyperplasia without overt morphologic evidence of involvement by lymphoma. Immunoperoxidase staining of the marrow biopsies with antibodies to CD20 and erythroid-associated antigens revealed involvement by large B-cell lymphoma morphologically resembling the early pronormoblasts. In both cases there was prominent, but not exclusive, intravascular/intrasinusoidal lymphomatous marrow infiltration. These cases represent an unusual variant of large B-cell lymphoma with distinctive patterns of splenic and BM involvement. Furthermore, they underscore the difficulties in identifying intrasinusoidal marrow infiltration by lymphoma in H&E-stained biopsy slides and demonstrate that this pattern of marrow infiltration may be seen in cases of large B-cell lymphoma distinct from the intravascular variant.