ERBB2 and cancer: Many of the tumors studied here have several driver mutations that are found in all tumor cells—all PIK3CA and TP53 mutations, all ERBB2, MYC, and CCND1 amplifications, all somatic loss of the wild-type BRCA1 and BRCA2 alleles among these 21 cancers can be placed unequivocally on the shared trunk of the phylogenetic tree.