Patients with HR-positive–ERBB2-negative cancer constituted 53.9% of the CSCO BC and 75.5% of the Flatiron databases; those with HR-positive–ERBB2-positive cancer, 15.9% of the CSCO BC and 12.0% of the Flatiron databases; those with HR-negative–ERBB2-positive cancer, 14.3% of the CSCO BC and 3.6% of the Flatiron databases; and those with triple-negative cancer, 15.9% of the CSCO BC and 8.9% of the Flatiron databases. This evidence concerns the gene ERBB2 and breast cancer.