Histopathological analysis revealed the following: Right breast: invasive ductal carcinoma (Estrogen receptor (ER) >90%, Progesterone receptor (PR) 60%, Human epidermal growth factor receptor 2 (Her2) 1+, Ki-67 10-20%), pathological stage pT2N0Mx; Left breast: predominantly ductal carcinoma in situ with focal invasive ductal carcinoma (ER <1%, PR <1%, HER2 3+, Ki-67 40%), pathological stage pT1bN0Mx (Table 1). Here, ESR1 is linked to invasive ductal breast carcinoma.