ESR1 and invasive ductal breast carcinoma: On the 16th of June, she underwent an ultrasound-guided core biopsy confirming an invasive ductal carcinoma of the breast with negative expression of hormone receptors (Estrogen Receptor (ER) 0% Progesteron Receptor (PgR) 0%), high proliferation index (Ki67 70%–80%), HER2 score 1+ with focal 2+ in 10%–15% of neoplastic cells (fluorescence in situ hybridization—not amplified).