PIK3CA and neoplasm: Figure 1b shows the proportions of tumours with amplifications (defined here as 5+ gene copies) and HDs or loss of heterozygosity (LOH) of the Mut-driver genes affected by CNAs in at least 1% of either ER+ or ER− tumours. Amplification of the known oncogenes KRAS, PIK3CA and AKT1 was more common in ER− tumours (3.9%, 2.7%, 1.2% respectively). We identified LOH events in 96.0% tumours that harboured CDH1 mutations, and in 85.4% of TP53-mutant tumours (Supplementary Fig. 5).