Table 4.

Definition of different surrogate subtyping classifications for ER+/HER2– breast cancer tumours

Clinicopathological surrogate definition	Characteristics
St. Gallen 2013 [11]
Luminal A-like	Low Ki67 (< 20%) and high PR (≥ 20%)
Luminal B-like	High Ki67 (≥ 20%) and/or low PR (< 20%)
Maisonneuve [12]
Luminal A-like	Low Ki67 (< 14%) or Intermediate Ki67 (14–19%) and high PR (≥ 20%)
Luminal B-like	High Ki67 (≥ 20%) or Intermediate Ki67 (14–19%) and low PR (< 20%)
St. Gallen 2017 [3]
Luminal A-like	High ER/PR, clearly low Ki67, HG1
Intermediate	Uncertainties persist about risk and degree of responsiveness to endocrine and cytotoxic therapies
Luminal B-like	Lower ER/PR, clearly high Ki67, HG3
Grade-based classification
Luminal A-like	HG1 or HG2 and low Ki67 (< 14%) or HG2 and intermediate Ki67 (14–19%) and high PR (≥ 20%)
Luminal B-like	HG3 or HG2 and high Ki67 (≥ 20%) or HG2 and intermediate Ki67 (14–19%) and low PR (< 20%)

ER oestrogen receptor, HER2 human epidermal growth factor receptor 2, HG histological grade, PR progesterone receptor