ERBB2 and breast cancer: No statistically significant differences were observed in the FGA of metastatic mixed mucinous, micropapillary, or metaplastic BCs compared to their primary counterparts, or to age-, menopausal status-, and ER/HER2 status-matched metastatic IDC-NSTs (Supplementary Fig. 4c, –e), potentially due to the small sample size of special types of BC other than ILCs analyzed in the study.