Figure 4

Evaluation of a 3 year-old girl with pancytopenia. A. Bone marrow core biopsy (40×) showing sheets of lymphoblasts. B-C. Representative flow cytometry histograms. The CD45(dim) gated population contained excess and abnormal B-lymphoblasts (85% of the total), positive for CD10, CD13, CD19, CD22, CD34, CD38, HLA-DR, plus intracellular CD79a, intracellular CD22, and TdT. D. Abnormal composite female karyotype with monosomy 16, trisomy 21, and deletions of 6q and 9q. E. FISH analysis detected the ETV6-RUNX1 (TEL-AML1) fusion, indicative of t(12;21) translocation. In addition, 4.4% of these abnormal cells showed an extra copy of the RUNX1 locus, suggestive of an underlying +21q.