ESR1 and breast cancer: It has previously been reported that the breast cancer of patients younger than 35 years old is more invasive, leading to poor prognosis.16 In this study, the positive expression rates of ER, PR, EGFR and p53 in the two groups did not differ significantly (P>0.05), whereas the rates of p63, CK5/6, CK14 and CK17 in the elderly group were significantly higher than those of the youth group (P<0.05).