Bone marrow biopsy. (A) Hematoxylin and eosin stain shows hypercellular for the age (80%-90%) bone marrow with increased elements of all 3 lineages. Reticulin stain shows no bone marrow fibrosis (data not shown). Anti-CD3 (B) and anti-CD20 (C) antibodies show scattered small T cells and B cells, respectively; no clusters of B cells and no large B cells are detected. (D) Anti-CD11c antibody represents increased myeloid elements. (E) Anti-CD71 antibody highlights increased erythroid elements. (F) Anti-CD61 antibody demonstrates markedly increased left-shifted megakaryocytes; no atypical megakaryocytes or megakaryocyte clustering is detected. Scale bars, 200 μm.