The data of a total of 1349 primary breast tumors (684 from patients with ER-positive (ER+) status and 221 with ER-negative (ER-) status) are given, including the clinical variables (grade (nominal), tumor stage (ordinal), human epidermal growth factor receptor 2 (HER2) status (binary), tumor size (numeric), progesterone receptor status (binary)) and CNA measurements. This evidence concerns the gene ERBB2 and breast neoplasm.