Pattern of recurrence of early breast cancer is different according to intrinsic subtype and proliferation index

Breast Cancer Research

Table 1 Immunohistochemical definition of breast cancer intrinsic subtypes according to four or six biomarkers ^a

Definition and subtype	ER	PR	HER2	Ki-67	CK5/6	EGFR
Definition of positive result	>1% of tumor nuclei	>1% tumor nuclei	HercepTest score 3+ or 2+ with CISH amplification ratio >2.2	≥14% of tumor nuclei	Any cytoplasmic or membranous staining	Any cytoplasmic or membranous staining
Subtype 4 biomarkers
Luminal A	ER + or PR+		Negative	Negative	–	–
Luminal B	ER + or PR+		Negative	Positive	–	–
HER2-enriched	Any	Any	Positive	Any	–	–
Triple-negative	Negative	Negative	Negative	Any	–	–
Subtype 6 biomarkers
Luminal A	ER + or PR+		Negative	Negative	Any	Any
Luminal B	ER + or PR+		Negative	Positive	Any	Any
Luminal HER2	ER + or PR+		Positive	Any	Any	Any
HER2-enriched	Negative	Negative	Positive	Any	Any	Any
Basal-like	Negative	Negative	Negative	Any	CK5/6-positive EGFR-positive
TNP nonbasal	Negative	Negative	Negative	Any	Negative	Negative

^aCISH, chromogenic in situ hybridization; CK, cytokeratin; EGFR, epidermal growth factor receptor; ER, estrogen receptor; HER2, human epidermal growth factor receptor 2; PR, progesterone receptor; TNP, triple-negative phenotype.

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