We then report the first large-scale ‘pan-cancer’ analysis of copy-number alterations on an absolute basis, across 3,155 cancer samples, representing 25 diseases with at least 20 samples. The analysis reveals that whole-genome doubling events occur frequently during tumorigenesis, ultimately resulting in mature cancers descended from doubled cells, bearing complex karyotypes. Despite evidence that genome doublings can result in genetic instability and accelerate oncogenesis 25,13,26 the incidence and timing of such events had not been broadly characterized in human cancer.
