The 100 patients are plotted along the x axis. The upper plot shows the number of structural rearrangements (y axis) in each tumour. The lower plot shows which chromosomes (y axis) harbour clusters of breakpoints. The distribution of breakpoints (events per Mb) within each chromosome for each sample was evaluated using two methods to identify clusters of rearrangements or chromosomes which contain a large number of events. Method 1: chromosomes with a significant cluster of events were determined by a goodness-of-fit test against the expected exponential distribution (with a significance threshold of <0.0001). Chromosomes which pass these criteria are coloured blue. Method 2: chromosomes were identified which contain significantly more events per Mb than other chromosomes for that patient. Chromosomes were deemed to harbour a high number of events if they had a mutation rate per Mb which exceeds 1.5 times the length of the interquartile range from the 75th percentile of the chromosome counts for each patient. Chromosomes which pass these criteria are coloured orange. Chromosomes which pass both tests they are coloured red. These criteria show that the unstable tumours which contain many events often have significant clusters of events. In contrast locally rearranged tumours are associated with both clusters of events and a high number of events within that chromosome when compared to other chromosomes.