LHP thymic lymphomas harbor translocations that arise from spontaneous and programmed DNA breakage. (A) LHP tumors exhibit clonal and nonclonal chromosomal abnormalities. Spectral and 4,6-diamidino-2-phenylindole (DAPI) images of a representative metaphase spread prepared from LHP tumor 111 (top panels) and the karyotype table (bottom panel) of this metaphase. Arrows indicate clonal and nonclonal translocations. Circles represent chromosome fragments. (B) LHP thymic lymphomas harbor clonal translocations. Shown are spectral and computer-classified images of the clonal translocations observed in each of the 5 LHP tumors (nos. 312, 891, 111, 649, and 67) analyzed by SKY. The identities of the chromosomes participating in these translocations are indicated. (C) LHP thymic lymphoma 67 contains a Tcrα/δ:c-myc translocation. Shown are representative FISH and chromosome paint analyses of LHP tumor 67 for potential involvement of Tcrα/δ and c-myc loci in the clonal t(2;14) and t(14;15) translocations. Each set of panels contains green paints specific for chromosome 14 or chromosome 15, the same metaphases with red Tcrα/δ or c-myc FISH probes, and merged images. Slides were counterstained with DAPI to visualize chromosomes.