Figure 4

Derivative chromosomes for the reciprocal t(2;8) IGK- MYC translocation in Burkitt-like lymphoma. (A) Full length reads mapping to IGK and MYC loci on der(2) and split-reads mapping to IGK and MYC loci on both der(2) and der(8). Red segments in the bottom panel indicate IGKJ segments. Full length reads all map to the negative strand indicative of inversion. Split-reads map in opposite orientations also consistent with inversion. The gaps between pink and blue split-reads pileups in the left and right panels cover sequence deleted before recombination. This includes a 252 bp deletion from der(8) and a 317 bp deletion from der(2). (B) The rearrangements were confirmed by Sanger sequencing, with the recovered sequences matching the junction spanning sequences found with split-reads. The split-read sequences are shown aligned to the two sequences present in the reference genome (hg19) from each junction. Aligned nucleotides are shown in gray and a mismatch between the reference and the sample is shown in white. (C) This tumor had many histologic features of a Burkitt lymphoma, consistent with activation of the MYC oncogene. A hematoxylin and eosin stained section shows a monotonous population of round, medium sized B-cells with large nuclei and variable cytoplasmic retraction. Intermixed macrophages with cellular debris (tingible body macrophages) impart a starry sky appearance. Numerous mitotic figures were seen. (D) Immunohistochemistry showed nuclear Ki67 proliferation antigen staining in a high percentage of the cells (brown). (E). The cells showed a mature germinal center cell phenotype with CD20, CD10, BCL6, restricted expression of kappa surface immunoglobulin, and no TdT. They were not immunoreactive for BCL2 (shown; blue counterstain).