ESR1 and breast neoplasm: In a database of more than 3,300 primary breast tumors retrieved from multiple public datasets (Figure S1 and Table S1 in Additional file 1), we observed a high proportion of well characterized ER+/HER2- subtype (48%) and lower proportions of well characterized ER-/HER2- (20%) and HER2+ (12%) subtypes (Figure 2), which concurs with the literature [15-17].