ESR1 and invasive ductal breast carcinoma: The biopsy confirmed a pathological diagnosis of invasive ductal carcinoma, no special type (NST), poorly differentiated (G3), estrogen receptor (ER) positive, progesterone receptor (PgR) positive, and HER2-negative, immunohistochemistry (IHC) score = 0, with a Ki-67 proliferation index of 70% (Figure 2).