interstitial (31.5%) spanning neither telomere nor centromere, while an additional small proportion (1.8%) spanned the centromere or had more complex structure (e.g. distinct events involving both telomeres, but not the whole chromosome). The majority of interstitial events were mosaic copy-loss (91.6%), which was most frequently observed within specific regions of chromosomes 13q and 20q (Figure 2). We observed 69 individuals (46 cancer cases and 23 cancer-free individuals) with clonal mosaic events on multiple chromosomes. The distribution of the number of clonal mosaic chromosomal events per individual is shown in Supplementary Table 3. Among cancer-free individuals, the greatest number observed was 5 mosaic chromosomal events, whereas six individuals with cancer had greater than 5 events, including two individuals with gastric cancer who each had 20. A list of mosaic events with phenotype data is available as Supplementary Data.
