Fig. 1

Initial and post treatment bone marrow evaluation. Bone marrow findings pre- (A–C) and post- (D) treatment. A The hematoxylin and eosin stained bone marrow core biopsy, ×20 objective magnification, shows a paratrabecular lymphoid aggregate (dashed line). B CD20 immunohistochemical stain, ×20 objective magnification, demonstrates that the lymphocytes in the aggregate are B-cell predominant (dashed line). The inset shows flow cytometry plots, gated on lymphocytes. T cells are shown in aqua, and B cells are shown in magenta. The B cells are uniformly kappa expressing, supporting the presence of a clonal B-cell population. Additional flow cytometry studies confirmed that the population lacked expression of CD5 and CD10 (data not shown). C A bone marrow aspirate prior to treatment is shown, ×60 objective magnification. The granulocyte to erythroid ratio was increased by differential count (> 15:1). Residual collections of erythroid precursors showed maturational arrest, with early erythroid precursors (labeled E, corresponding to pronormoblasts). Late erythroid precursors (polychromatophilic and orhochromatic normoblasts) were not identified. D A post treatment bone marrow aspirate is shown, ×60 objective magnification, in contrast to the pre-treatment sample, a full spectrum of maturing erythroid precursors was now present, highlighted by abundant late erythroid precursors (labeled L)