ERBB2 and breast cancer: This discrepancy between HER2-low and HER2-0 breast cancers in the HR-negative subgroup was also implied by several specialized TNBC subtyping systems with the different assignments of molecular subtypes, including FUSCC-TNBC subtype10, Burstein’s subtype17, Lehman’s subtype18 and Quist’s TNBC subtype19 (Table 2).