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Body: Background: Estrogen receptor (ER) positive HER2-negative breast cancer comprises 75–80% of all breast cancer. Thisfraction is even higher (>90%) in invasive lobular carcinoma (ILC). According to the St Gallen surrogate definitions of the intrinsicsubtypes, Ki67 and progesterone receptor (PgR) are used to classify these tumors as luminal A- and luminal B-like(HER2-negative). These guidelines
