ERBB2 and breast cancer: Consequently, the molecular subtypes of breast cancer can provide useful references for tumor heterogeneity, staging, new therapeutic targets, prognostic assessment, individualized treatment strategy, etc. According to the clinically widely used criteria formulated by the 12th St Gallen International Breast Cancer Conference (2011), breast cancer can be classified into four subtypes: luminal A, luminal B, triple negative, and HER-2 enriched (9).