Table I. Patient characteristics by HER2 immunohistochemical status.
*Genomic risk low: Oncotype RS ≤25, Mammaprint-low, Endopredict-low. Genomic risk high: Oncotype RS ≥26, Mammaprint-high, Endopredicthigh. #p-values (HER2-0 vs. HER2-low) were calculated using chi-square test for: age at diagnosis (≤50 vs. >50), genetic profile where checked (mutated vs. wild-type), histology (IDC vs. ILC and mixed), grade (grade 1, 2 or 3), Ki67 (0-20 vs. >20) and genomic risk where checked (low vs. high). HER2: Human epidermal growth factor receptor-2; ISH: in situ hybridization; GnRHa: gonadotropin-releasing hormone agonist; IDC: infiltrative ductal carcinoma; ILC: infiltrative lobular carcinoma.