ESR1 and neoplasm: To assess demographic and tumor related factors associated with IHC findings, we classified cases into four clinical treatment IHC groups by combined ER/PR status and HER2 status: ER-/PR-, HER2- (n=92; 46.7%), ER-/PR-, HER2+ (n=20; 10.1%), ER+/PR+, HER2- (n=76; 38.6%) and ER+/PR+, HER2+ (n=9; 4.6%).