Women with HER2-low breast cancers were older (relative to women with HER2-zero breast cancers) (75 yr+: 3822/20,636 (18.5%) vs. 1852/10,293 (18.0%); 65-74 yr: 5016/20,636 (24.3%) vs. 2365/10,293 (23.0%), p < 0.001), and tended to have public insurance at diagnosis (11,018/20,636 (53.4%) vs. 5330/10,293 (51.8%), p = 0.008). Here, ERBB2 is linked to breast cancer.