Figure 3. Atypical Burkitt lymphoma. Atypical cells infiltrating the bone marrow had large cytoplasmic vacuoles consistent with L3 morphology (3a, 3b, 3c). The cells were positively stained with CD20, CD79a, and Bcl-6, and were negative for MUM-1 and Bcl-2. The proliferation index examined by Ki-67 was around 100%.