Amplification and overexpression of CCND1 oncogene, encoding cyclin-D1 protein, is frequent in BC, more specifically within luminal A (29%), luminal B (58%), and human epidermal growth factor receptor 2 (HER2) enriched (38%) subtypes, while CCND2 or CCND3 amplification is rare. Here, ERBB2 is linked to breast cancer.