The following molecular subtypes of breast cancer (Group A1) were identified on the basis of molecular biology of cancer tissue: Luminal A (n = 7, 12.5%), Luminal B (human epidermal growth factor receptor 2 [HER2]–negative; n = 25, 44.6%), triple-negative (n = 23, 41%), and Luminal B (HER2-positive; n = 1, 1.9%). This evidence concerns the gene ERBB2 and breast cancer.