ERBB2 and breast cancer: One of the latest and most accepted surrogate definitions has been the one proposed in the St Gallen International Breast Cancer Conference in 2013, upon which luminal A-like tumors are ER+, HER2−, with low Ki-67 expression (<20 %) and high PgR levels (≥20 %); luminal B-like (HER2-negative) tumors are ER+ and HER2− with high Ki-67 expression (≥20 %) or low PgR levels (<20 %); and luminal B-HER2 tumors are ER+ and HER2+, regardless PgR or Ki-67 expression.