To exclude the influence of different BC molecular subtypes (HR+/HER2-, luminal A; HR+/HER2+, luminal B; HR-/HER2+, HER2-enriched; HR-/HER2-, triple-negative) on the stability and accuracy of the model, Kaplan–Meier curves for OS were generated for low-, middle-, and high-risk patient groups in the training set, the validation set, and the four molecular subtypes. This evidence concerns the gene ERBB2 and breast cancer.