ERBB2 and breast cancer: Nevertheless, our findings are in accordance with the observations of the TCGA network, who described a high frequency of TP53 (55%) and PIK3CA (31%) mutations, and an low frequency of mutations in RUNX1 (1%), PTEN (0%), NCOR (0%) and CDH1 (3%) in 75 clinically HER2‐positive breast cancers (Koboldt et al., 2012).