A recent report that analyzed a cohort of 2310 patients pooled from four clinical trials demonstrated the distinct biology, clinicopathological features, therapeutic response, and clinical outcome of HER2-low breast cancers (defined by IHC 1+/2+ with FISH-negative result) as compared with HER2-zero, suggesting that HER2-low should be recognized as a new subtype of breast cancer [21]. Here, ERBB2 is linked to breast cancer.