ESR1 and invasive ductal breast carcinoma: She returned 3 years later with T1c N0 M0, grade 3 estrogen receptor (ER) positive, progesterone receptor (PR) positive, HER2/neu negative, and Ki-67 20–25% infiltrating ductal carcinoma of the superior-medial quadrant of the right breast and underwent additional partial mastectomy and sentinel node biopsy followed by chemotherapy and radiation therapy.