ESR1 and invasive ductal breast carcinoma: A 39-year-old G2P2 female discovered a palpable mass in the right breast while breastfeeding her 7-month-old child, leading to the diagnosis of a high-grade ER+ (80% moderate staining), human epidermal growth factor receptor 2-negative (ErbB2-) invasive ductal carcinoma with axillary nodal involvement.