ESR1 and breast cancer: The patient was in follow-up since 1996 for a previous BC located in the upper outer quadrant of the same breast: a grade 3 invasive breast carcinoma of no special type (IBC-NST; pT1cN0M0), hormone receptor positive (Allred score: ER 6/8 and PR 7/8) and treated by lumpectomy with axillary lymph node dissection and adjuvant chemotherapy (a-CT) (six cycles of cyclophosphamide, methotrexate, and 5-fluorouracil) followed by radiotherapy (breast 50 Gy + 16 Gy boost) without endocrine therapy.