Use of the core biopsy is foundational to treatment planning, to identify patients with early‐stage ER+ HER2− breast cancer and low‐intermediate grade tumors, lobular histology, or low‐risk genomic assays results for whom neoadjuvant endocrine treatment can be administered when surgery is deferred.1, 2, 3, 4. Here, ESR1 is linked to breast carcinoma.