CYP19A1 and breast cancer: In the present study, we demonstrated that, in LN-negative, HR-positive breast cancer patients, premenopausal women carrying the CYP19 genetic polymorphism haplotype AASA had a significantly poorer DDFS, DFS, and OS than those without haplotype AASA. Even in patients who received chemotherapy, haplotype AASA remained a negative prognostic factor for DDFS, DFS, and OS.